Preheat the oven: Set to 375°F (190°C).
Grease a 9x13-inch baking dish with a little oil or butter.
Crisp the bacon: In a large skillet, cook the chopped bacon over medium heat until crisp. Remove to a paper towel–lined plate. Reserve 1–2 tablespoons of bacon fat in the pan.
Sauté aromatics: Add the diced onion to the pan with bacon fat and a pinch of salt.
Cook 3–4 minutes until softened. Add minced garlic and cook 30 seconds more.
Brown the beef: Add ground beef to the skillet. Season with salt, pepper, smoked paprika, onion powder, and garlic powder.
Cook until browned, breaking it up with a spatula. Drain excess fat if there’s a lot, but leave a little for flavor.
Make the burger-style sauce: Stir in tomato paste, sugar-free ketchup, yellow mustard, and Worcestershire. Mix until the beef is evenly coated and glossy.
Taste and adjust salt and pepper.
Build the base: Spread the beef mixture evenly in the prepared baking dish. Sprinkle half the chopped pickles over the beef for tang in every bite.
Make the custard: In a bowl, whisk the eggs and heavy cream with a pinch of salt and pepper until smooth. This creates a creamy, quiche-like set that holds the casserole together.
Add the cheeses: Sprinkle 1 cup cheddar and 1/2 cup mozzarella over the beef layer.
Pour the egg mixture evenly over the top, tilting the dish slightly to distribute.
Top and bake: Scatter the remaining cheeses and most of the crispy bacon on top, reserving a bit for garnish. Bake for 20–25 minutes, until the center is set and the top is bubbling and lightly golden.
Rest and finish: Let it rest 8–10 minutes. Garnish with remaining bacon and remaining chopped pickles.
Add optional shredded lettuce, diced tomato, or green onions right before serving for a “loaded burger” effect.
Serve: Cut into squares and plate. A drizzle of sugar-free ketchup or mustard on top is a nice touch.