Preheat your oven to 375°F (190°C) and lightly grease your baking dish

Heat olive oil in a large skillet over medium heat

Add chopped onion and sauté until soft and translucent

Stir in minced garlic and cook for about 30 seconds until fragrant

Add ground beef and break it apart using a spatula

Cook until fully browned and no pink remains

Drain excess grease to prevent a greasy casserole

Add taco seasoning and mix thoroughly into the beef

Pour in diced tomatoes with green chilies and stir well

Let the mixture simmer for 3–4 minutes to develop flavor

Remove from heat and allow it to cool slightly

In a mixing bowl, whisk together eggs, heavy cream, and sour cream until smooth

Add half of the shredded cheddar and mix into the egg mixture

Transfer the beef mixture into the prepared baking dish

Spread evenly to form the base layer

Pour the creamy egg mixture evenly over the beef

Sprinkle mozzarella and remaining cheddar cheese on top

Add sliced jalapeños evenly across the surface if using

Place the dish in the oven and bake for 25–30 minutes

Bake until the center is set and the cheese is melted and golden

Switch to broil for 2–3 minutes for a lightly crispy top

Remove from oven and let it rest for 5–10 minutes before slicing

Garnish with fresh cilantro and serve warm