Cook the beef:
In a large skillet, cook the ground beef over medium heat until browned. Drain excess fat. Add the chopped onion and garlic, and cook for 2–3 minutes until softened.

Season the beef:
Stir in the taco seasoning and beef broth. Let the mixture simmer on low heat for about 5–7 minutes until the liquid reduces and thickens. Season with salt and pepper to taste. Remove from heat and set aside.

Prepare the tortillas:
Heat the vegetable oil in a separate skillet over medium heat. Lightly fry each tortilla for about 30 seconds per side, just enough to soften them (not crisp). Place fried tortillas on paper towels to drain excess oil.

Assemble the enchiladas:
Preheat your oven to 350°F (175°C). Spread a small amount of enchilada sauce in the bottom of a baking dish to prevent sticking. Next, dip each tortilla in the enchilada sauce, fill with a generous spoonful of the beef mixture, and sprinkle with both cheeses. Roll up the tortilla tightly and place it seam-side down in the baking dish.

Top with sauce and cheese:
Once all the tortillas are arranged in the dish, pour the remaining enchilada sauce over the top. Sprinkle with the remaining shredded cheddar and Monterey Jack cheese.

Bake:
Cover the dish with foil and bake for 20 minutes. Remove the foil and bake for an additional 5–10 minutes until the cheese is melted and bubbly.

Serve:
Remove from the oven, and let cool for a few minutes before serving. Garnish with fresh cilantro, sour cream, or shredded lettuce if desired. Serve hot.