For the béchamel sauce:
- 1 stick butter
- 8 tablespoons flour
- 2 quarts milk
- Salt and pepper
- Freshly grated nutmeg, to taste
- 4 large egg yolks, beaten
- About 2 cups grated Parmigiano Reggiano cheese
For the green filling:
- 1/4 cup extra virgin olive oil (EVOO)
- 1 1/2 pounds sweet Italian sausage
- 2 fresh red chili peppers, seeded and finely chopped
- 8 cloves garlic, chopped
- 1/2 cup dry white wine or chicken stock
- 2 packages chopped frozen spinach, defrosted and separated
- 2 bunches broccoli rabe, chopped and par-boiled 8 minutes, drained
- Salt and pepper
For the white filling:
- 3 cups ricotta cheese
- 2 egg yolks, beaten
- About 1/2 cup grated Parmigiano Reggiano cheese
- 1/4 cup flat- eaf parsley, finely chopped
- 2 boxes flat, no-bake lasagna sheets, such as Barilla
Pre-heat the oven to 375°F.
For the white sauce, melt the butter over medium to medium-high heat in a saucepot. Whisk in the flour, cook for 1-2 minutes, then whisk in the milk and season with salt, pepper and a little nutmeg. Let thicken to coat a spoon and adjust the seasoning. Temper the egg yolks with a ladle of sauce, then add them into to the pot. Stir in the cheese and remove from the heat.
Meanwhile, for the green layer, heat the EVOO in a large skillet. Brown and crumble the sausage, then add the chili peppers and garlic. Cook to soften; deglaze the pan with wine or stock and add in the rabe and spinach. Combine and season with salt and pepper, to taste.
Combine the ricotta with the egg yolks, grated cheese and parsley.
Soak the lasagna noodles for 4-5 minutes in warm water. Drain and separate.
Grease a 9-inch x13-inch baking dish with EVOO. Add half of the white sauce then a layer of lasagna pasta sheets, half of the green filling, another layer of lasagna sheets, all of the ricotta, lasagna sheets, the remaining green filling, lasagna sheets and the remaining béchamel. Bake for 1 hour, until golden on top. Let stand for 15-20 minutes before cutting.