Lasagne Bolognese

One package of fresh pasta sheets
Freshly grated reggiano parmigiano cheese
Butter

One batch of Bolognese (we often double or triple the recipe and freeze it):
1 tablespoon olive oil
3 tablespoons butter
Small yellow onion, chopped into small dice
2 celery ribs, chopped into small dice
2 large carrots, peeled and chopped into small dice
1/3 pound ground chuck
1/3 pound ground pork
1/3 pound ground veal
1 cup whole milk
Whole nutmeg
1 cup dry white wine
1 28 ounce can whole San Marzano tomatoes, drained

Put the oil, butter and onion in a large pot over medium heat.  Cook until the onion is translucent, stirring occasionally.  Add the celery and carrots, cook for about 2 minutes, stirring the vegetables.
Add the ground meats to the pot with a large pinch of kosher salt and a few grindings of black pepper.  Crumble the meat with the back of a wooden spoon and cook until it has lost its raw color.
Add the milk to the pot and adjust the temperature to a gentle simmer.  Simmer until all of the liquid has bubbled away.  Add a tiny grating of fresh nutmeg and stir the pot.  Add the wine and simmer until all of it has evaporated, stirring occasionally.
Add the tomatoes, crushing them in your hand as you add them to the pot.  Stir well to combine all the ingredients.  When the sauce begins to bubble, turn the heat down as low as possible and simmer very very gently for 3 hours.  Add water (1/2 at a time) if the sauce appears to be drying out.  Taste and correct for salt.

Béchamel Sauce:
3 cups whole milk
6 tablespoons butter
4 1/2 tablespoons flour
1/4 teaspoon salt

Heat the milk just to the verge of boiling.  In a separate pan, melt the butter over medium low heat.  Add the flour and cook, stirring, for about 2 minutes.  Slowly add the warm milk to the flour/butter mixture (the roux).  Add the salt and stir until the sauce is the texture of heavy cream.

Preheat the oven to 400 degrees.  Smear the bottom of a lasagne pan with butter and spoon in some béchamel sauce to coat the bottom.  Line the bottom with a single layer of the pasta
Combine the bolognese sauce with béchamel sauce.  Spread a layer on the pasta.  Sprinkle with parmesan cheese.  Add another layer of the pasta and repeat, layering, until all of the pasta and sauce are gone.  Finish with a thin layer of sauce on the top layer and sprinkle with cheese.  Dot the top with butter.
Bake in the top rack of the oven for 10 to 15 minutes.