Lasagna Bolognese

Rag�:
1/4 cup extra-virgin olive oil
2 medium onions, finely chopped
1 carrot, finely chopped
4 stalks celery, finely chopped
5 cloves garlic, sliced
1 pound veal, ground
1 pound pork, ground
4 ounces pancetta, ground
1 8-ounce can tomato paste
1 cup milk
1/2 cup white wine
1 teaspoon fresh thyme leaves
Salt and freshly ground black pepper

B�chamel:
5 tablespoons unsalted butter
1/4 cup flour
3 cups milk
2 teaspoons salt
1/2 teaspoon freshly grated nutmeg

Lasagna:
3/4 to 1 pound fresh pasta sheets, about 7 by 4 inches, or dried lasagne noodles blanched for 6 minutes and refreshed
1 cup freshly grated Parmigiano-Reggiano
Oil for brushing

Rag�: In a large heavy-bottom saucepan, heat olive oil. Add onion, carrot, celery, and garlic, and sweat over medium heat for about 5 minutes, until vegetables are translucent. Add veal, pork, and pancetta to the vegetables, and brown over high heat, stirring to keep the meat from sticking together. Add the tomato paste, milk, wine, thyme, and 1 cup water, and simmer over medium-low heat for 1 to 11/2 hours (if the rag� becomes too thick, add a little more water). Season to taste with salt and pepper, and remove from heat.

B�chamel: Melt the butter in a medium saucepan, add the flour, and whisk until smooth. Cook over medium heat, stirring regularly, until the mixture turns golden brown, about 6 to 7 minutes.

Meanwhile, heat the milk in a separate pan until it is just about to boil. Add the milk to the butter mixture, 1 cup at a time, whisking continuously until the sauce is very smooth. Bring to a boil and cook for 30 seconds longer. Remove from the heat and season with salt and nutmeg.

Assembly: Preheat the oven to 375 degrees. Brush a 9-by-13-inch glass baking dish with melted butter or oil, and layer in the following order from the bottom: rag�, pasta, b�chamel, and grated cheese (saving about 1 cup b�chamel for last topping), making 3 to 4 layers of pasta, finishing with rag�, b�chamel, and 1/4 cup of the Parmigiano-Reggiano sprinkled over the top. Bake in the oven for 45 minutes, until the top is golden brown and the casserole is bubbling. Remove from the oven, allow to cool for 20 minutes, slice, and serve.