Preheat oven to 375°F (190°C).
Heat a large skillet over medium heat and add ground beef.
Cook beef until browned, breaking it apart as it cooks.
Add chopped onion and sauté until softened.
Stir in garlic, chili powder, paprika, salt, and black pepper.
Remove skillet from heat and mix in sour cream and milk.
Spread half of the crushed Doritos in the baking dish.
Spoon beef mixture evenly over the Doritos.
Sprinkle cheddar and mozzarella cheese on top.
Add remaining Doritos over the cheese layer.
Bake for 25 minutes until cheese is melted and bubbly.
Remove from oven and garnish with fresh parsley before serving.