In a food processor add the onion, carrot and celery and pulse until finely chopped. If you aren’t using a food processor then finely chop the onions, carrots and celery.
In a Dutch oven or large pot heat the oil over medium high heat. Add the vegetables and cook until everything has softened, about 5 minutes. Add the garlic and bay and cook for another 1 minute.
Add the ground pork and beef and cook until browned and cooked throughout. Add the wine and cook until it has reduced by half. Then add the milk and cook until it has reduced by half.
Add the crushed tomatoes, salt and pepper. Reduce to a simmer and cover. Cook for an hour.
Making the bechamel sauce
In a saucepan heat the butter over medium-high heat. Add the flour and cook for 2 minutes. Gradually add the milk, nutmeg, and salt and cook until thickened and set aside.
Preparing the pasta
Bring a pot of water to a boil and cook the pasta until al dente.
If you are using fresh pasta roll out the dough to the thinnest setting and add to the boiling water. Cook for 2 minutes.
Set the pasta on a plate with a little water in it to keep them from sticking.
Making the lasagna
Preheat the oven to 350°F, 177°C, or gas mark 4.
Spread a small amount of bechamel and/or Bolognese sauce on the bottom of the dish. Place the first layer of pasta across the bottom of the dish. Next add about a cup of Bolognese sauce.
Add about a ½ cup of bechamel sauce. Sprinkle mozzarella on top and repeat until you have filled the baking dish.
Top the final layer with the remaining mozzarella and the parmesan cheese.
Cover with aluminum foil and bake for 30 minutes, remove the foil and bake for another 15 minutes.
Allow to cool for at least 15 minutes before slicing.