Preheat the Oven: Preheat your oven to 350 degrees F (175 degrees C) and lightly grease a pie dish or oven proof skillet.
Cook the Beef: Heat oil in a frying pan over medium heat; fry chopped onions and garlic until it smells. Stir in the ground beef and cook until no longer pink. Drain excess grease.
Season the Meat: Add taco seasoning and a splash of water. Let simmer for 2–3 minutes. Remove from heat.
Layer the Pie Dish: Transfer the seasoned beef to the prepared pie dish and spread out to cover the bottom.
Make the Egg Mixture: In a bowl, in another pot, whisk together the eggs, heavy cream, salt and pepper. Pour over the beef layer.
Add Cheese: Sprinkle with shredded cheddar and mozzarella cheese.
Bake: Bake, uncovered, until the center is set and top is golden and bubbly, about 30 minutes.
Cool and Serve: Allow the pie to sit for 5 minutes before cutting. Top with additional toppings if desired and serve warm.