1. Prepare the American Lamb and Spinach Filling:

In a large skillet, heat the olive oil over medium heat. Add the chopped onion

and cook until softened, about 5 minutes. Add the minced garlic, dried oregano, red pepper flakes and 3/4 teaspoon kosher salt.. Cook for another 1-2 minutes until fragrant.

Add the ground American lamb and cook until browned, breaking it up with a spoon as it cooks, about 7-8 minutes. Season with additional 3/4 teaspoon kosher salt and freshly ground black pepper. Add the chopped spinach and cook until wilted, about 3-4 minutes. Remove from heat and set aside.

2. Prepare the Béchamel Sauce:

Add the flour and whisk continuously for about 2-3 minutes, until the mixture is golden and bubbling. Gradually add the warmed milk, whisking constantly to prevent lumps, until the sauce is smooth and thickened, about 5-7 minutes. Stir in the ground nutmeg and Parmesan cheese. Season with salt. Remove from heat.

3. Prepare the Ricotta Mixture:

In a bowl, combine the ricotta cheese, beaten egg and 1/2 cup grated parmesan cheese. Season with salt and pepper. Mix well and set aside.

4. Assemble the Lasagna:

Preheat your oven to 375°F (190°C). Spread a thin layer of béchamel sauce on the bottom of a 9x13-inch baking dish. Place a layer of lasagna noodles over the sauce. Spread 1/3 of the ricotta mixture over the noodles. Spoon 1/3 of the lamb and spinach filling over the ricotta. Drizzle 1/3 of the remaining béchamel sauce over the filling. Repeat the layers two more times, ending with a final layer of béchamel sauce. Sprinkle the top with the mozzarella and finally the grated Parmesan cheese.

5. Bake the Lasagna:

Cover the baking dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 20-25 minutes, until the top is golden and bubbling. Let the lasagna rest for 10-15 minutes before serving.