01 - Preheat oven to 425°F. Line a large baking sheet with parchment paper and lightly grease a 9x13-inch baking dish.
02 - Arrange cabbage rounds on the prepared baking sheet. Brush both sides with 2 tbsp olive oil and season with salt and pepper. Roast for 20-25 minutes, flipping halfway, until edges are golden and crispy.
03 - Heat 1 tbsp olive oil in a large skillet over medium heat. Add onion and cook 3-4 minutes until softened. Add garlic and cook 1 more minute.
04 - Add ground beef and cook, breaking it up, until browned and cooked through, about 6-8 minutes. Drain excess fat if needed.
05 - Stir in ketchup, mustard, Worcestershire sauce, smoked paprika, oregano, garlic powder, onion powder, and salt and pepper to taste. Simmer for 2 minutes. Remove from heat.
06 - In a medium bowl, whisk together eggs and milk until fully combined.
07 - Layer half of the roasted cabbage in the prepared baking dish. Spread all of the beef mixture evenly over the cabbage. Top with the remaining cabbage.
08 - Pour the egg-milk mixture evenly over the casserole. Sprinkle the shredded cheddar cheese on top.
09 - Bake uncovered at 375°F for 15-20 minutes, until cheese is melted and bubbly and casserole is set.
10 - Let rest for 5 minutes before serving. Garnish with optional toppings such as sliced pickles, diced tomatoes, chopped green onions, or sesame seeds as desired.