In a large skillet, melt 2 tablespoons of butter or beef tallow over medium heat. Add 1½ pounds of ground beef and ½ pound of Italian sausage (if using). Cook until browned and crumbled (approximately 8–10 minutes), stirring occasionally. Season with sea salt and optional black pepper.

In a medium mixing bowl, combine 2 cups of whole milk ricotta cheese, 1 large egg, and ½ cup of grated Parmesan cheese. Mix until smooth, ensuring the egg is well incorporated.

Preheat your oven to 375°F (190°C). Grease a 9x13-inch baking dish with cooking spray or butter.

Begin layering your lasagna by adding a layer of the meat mixture to the bottom of the prepared dish. Top with mozzarella slices, half of the ricotta mixture, and a layer of shredded mozzarella. Repeat layers, finishing with mozzarella slices and remaining Parmesan on top.

Cover with aluminum foil and bake for 20 minutes. Remove foil and bake for another 15-20 minutes until bubbling and golden brown.

Remove from the oven and let rest for about 10 minutes before slicing.

Slice and serve warm, perfect with a side salad or low-carb vegetables.