The Best Steak Bite Tortellini with Fontina & Roasted Mushroom Blend Casserole

There’s something incredibly comforting about a hearty baked casserole that brings together tender steak bites, creamy cheese tortellini, and the earthy richness of roasted mushrooms. This Steak Bite Tortellini with Fontina & Roasted Mushroom Blend Casserole is a dish made for cozy evenings, Sunday family dinners, or any night when you crave indulgence without spending hours in the kitchen.

The inspiration for this recipe comes from the love of blending elegance with comfort. Tortellini, often seen in Italian kitchens, pairs beautifully with the depth of Fontina cheese—a nutty, buttery cheese that melts into a velvety sauce. Add in seared steak bites and roasted mushrooms, and you’ve got a dish that feels special enough for entertaining, yet practical enough to whip up after work. This casserole is more than just dinner—it’s a centerpiece that invites people to gather, share, and savor.

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Why You’ll Love This Recipe

• Comfort Food Upgrade: It’s like a cheesy baked pasta, but with steak and Fontina elevating it into a restaurant-worthy dish.

• Balanced Flavors: The umami from roasted mushrooms, the tenderness of steak, and the creaminess of tortellini create layers of flavor.

• Family-Friendly: Serves six generously, making it ideal for families or meal prepping.

• Versatile: Easily customizable with different cheeses, add-ins like spinach or caramelized onions, or even a crunchy breadcrumb topping.

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Ingredients You’ll Need

Here’s everything required to make this indulgent casserole:

• 1 ½ lbs sirloin or ribeye steak, cut into bite-sized cubes

• 2 tbsp olive oil

• 16 oz cheese tortellini (fresh or refrigerated)

• 3 cups mixed mushrooms (cremini, shiitake, portobello), sliced

• 3 tbsp butter

• 3 tbsp all-purpose flour

• 3 cups whole milk (or half-and-half for richer sauce)

• 2 cups shredded Fontina cheese

• 1 cup shredded mozzarella (optional, for topping)

• 1 tsp garlic powder

• ½ tsp thyme

• ½ tsp black pepper

• Salt, to taste

• Fresh parsley, for garnish

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Step-by-Step Instructions

1. Roast the Mushrooms

Start by preheating your oven to 400°F (200°C), which is the ideal temperature for coaxing out deep, savory flavors from mushrooms. Place your sliced cremini, shiitake, and portobello mushrooms in a large mixing bowl and drizzle them with one tablespoon of olive oil. Add a generous pinch of salt, freshly cracked black pepper, and thyme. Toss everything together so each mushroom slice is lightly coated.

Spread the mushrooms in a single layer on a parchment-lined baking sheet. This step is crucial—crowding them will cause the mushrooms to steam instead of roast. Slide the pan into the oven and let them cook for about 15–20 minutes, stirring once halfway through. You’ll know they’re ready when the edges are golden and slightly crispy, and the mushrooms have shrunk down in size.

Roasting mushrooms concentrates their natural umami, turning them from soft and mild into rich, meaty bites. This step gives the casserole a depth of flavor that you simply can’t get from raw or sautéed mushrooms.

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2. Sear the Steak Bites

While the mushrooms are roasting, prepare your steak. Heat the remaining tablespoon of olive oil in a large skillet over medium-high heat. Once the oil shimmers, add the cubed sirloin or ribeye steak in a single layer. Let the cubes sear undisturbed for about one minute on each side until a golden crust develops.

Don’t worry about cooking the steak all the way through—this quick sear is only about creating flavor. The high heat caramelizes the outside, locking in juices and ensuring each bite tastes savory and satisfying. Once browned, transfer the steak to a plate and set aside. They will finish cooking gently while the casserole bakes, preventing dry or overdone beef.

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3. Cook the Tortellini

Bring a large pot of salted water to a rolling boil. Add the cheese tortellini and cook them until just al dente, which is usually about one minute less than the package suggests. Drain immediately and set aside.

This undercooking step is intentional. Since the tortellini will continue to soften in the oven while absorbing the creamy Fontina sauce, starting with slightly firmer pasta ensures they don’t become mushy or fall apart during baking. Think of it as giving the pasta a little head start before the final stage.

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4. Make the Fontina Cream Sauce

In a medium saucepan, melt three tablespoons of butter over medium heat. Once melted, whisk in the flour to form a roux. Cook for 1–2 minutes to eliminate any raw flour taste. Gradually pour in the milk, whisking constantly to avoid lumps. Continue stirring until the sauce thickens to a silky consistency that coats the back of a spoon.

Lower the heat and stir in the shredded Fontina cheese. As the cheese melts, the sauce transforms into a velvety, rich base. Season with garlic powder, black pepper, and a pinch of salt to taste. The Fontina gives the sauce a nutty, buttery flavor that pairs beautifully with the tortellini, mushrooms, and steak.

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5. Assemble the Casserole

Grease a 9×13-inch baking dish with butter or cooking spray. Add the cooked tortellini, roasted mushrooms, and seared steak bites into the dish. Gently toss to distribute the ingredients evenly.

Next, pour the Fontina cream sauce over the top, using a spatula to spread it so every bite is coated. If you’re a cheese lover, sprinkle shredded mozzarella across the surface for extra gooeyness and a beautiful golden crust.

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6. Bake

Place the casserole uncovered in a preheated oven at 375°F (190°C). Bake for 20–25 minutes until the top is golden, bubbling, and irresistibly fragrant. This final step melds the flavors together and gives the dish its signature baked finish.

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7. Garnish & Serve

Once baked, remove the dish from the oven and let it rest for about five minutes. This short wait allows the sauce to settle slightly, making it easier to scoop and serve. Finish with freshly chopped parsley for a bright, fresh contrast to the richness.

Serve warm, and enjoy as the tender steak bites, creamy pasta, and roasted mushrooms come together in every forkful.

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Tips & Variations

• Extra Savory: Stir in caramelized onions or sun-dried tomatoes for even more depth.

• Cheese Lovers: Add Gruyère or Havarti for a more complex cheese profile.

• Crunchy Topping: Sprinkle buttered breadcrumbs over the top before baking for a crisp crust.

• Vegetable Boost: Fold in spinach, roasted red peppers, or even broccoli for a veggie-packed twist.

• Protein Swap: Substitute chicken breast, Italian sausage, or even shrimp for a different flavor direction.

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Serving Suggestions

This casserole is filling on its own, but pairing it with simple sides can transform it into a full feast. Consider:

• A crisp green salad with balsamic vinaigrette to cut through the richness.

• Garlic bread or warm focaccia for soaking up extra sauce.

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Storage and Reheating

One of the best things about casseroles is that they’re just as good the next day.

• Refrigerator: Store leftovers in an airtight container for up to 3–4 days.

• Freezer: Assemble the casserole but skip baking. Wrap tightly in foil and freeze for up to 2 months. Bake from frozen at 350°F, adding 15–20 minutes to the bake time.

• Reheating: Warm individual portions in the microwave or reheat the whole dish in the oven at 350°F until heated through.

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Nutritional Breakdown (Approx. per Serving)

While indulgent, this casserole offers a satisfying balance of protein, carbs, and dairy:

• Calories: ~550

• Protein: ~35g

• Carbohydrates: ~40g

• Fat: ~28g

• Fiber: ~3g

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Frequently Asked Questions

Can I make this casserole ahead of time?

Yes, this recipe is very make-ahead friendly, which makes it perfect for busy weeknights or entertaining. You can assemble the entire casserole a day in advance and keep it covered in the refrigerator. When you’re ready to serve, simply bake it as directed. Because it will be starting from a cold state, add an extra 5–10 minutes to the bake time to ensure everything is hot and bubbly in the center.

If you want to plan even further ahead, you can also freeze the casserole before baking. Wrap it tightly in plastic wrap and aluminum foil, then store it in the freezer for up to two months. When ready to cook, bake directly from frozen at 350°F, adding about 20 extra minutes to the cooking time. This makes it a great option for meal prepping or for keeping a “company-ready” dinner on hand.

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What if I can’t find Fontina cheese?

Fontina is a semi-soft Italian cheese known for its buttery, nutty flavor and smooth melting quality. If it’s not available at your local store, don’t worry—you have plenty of excellent substitutes. Gruyère brings a slightly sharper, more complex taste. Havarti is mild and creamy, making it a good match for families who prefer subtle flavors. Provolone also melts beautifully and gives the sauce a slightly smoky undertone.

For the best flavor balance, you can even use a blend—try mixing Gruyère and mozzarella or Havarti and Parmesan. The key is to choose a cheese that melts well and enhances the creaminess of the sauce.

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Do I have to use steak?

Not at all. While steak makes this casserole indulgent and special, it’s flexible enough to accommodate different proteins. If you prefer poultry, diced chicken breast or chicken thighs are excellent substitutes. For a heartier flavor, try using crumbled Italian sausage, which adds spice and richness to the dish.

Vegetarians can easily adapt this recipe by omitting the meat altogether and increasing the quantity of roasted mushrooms. The mushrooms provide a meaty texture and deep umami flavor, making the casserole just as satisfying without the beef.

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Can I use dried tortellini instead of fresh?

Yes, dried tortellini works as well, though it requires a slight adjustment. Cook it until just shy of al dente before adding it to the casserole, as it will continue cooking while baking. Fresh or refrigerated tortellini tends to deliver a softer, more tender bite, but dried pasta can be a great pantry-friendly alternative.

If using dried tortellini, make sure to salt your cooking water generously, since dried pasta benefits even more from seasoning during the boiling stage. Either option results in a delicious casserole—it just depends on what you have available.

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