Begin by cooking the vegetables.
In a large pot, sauté the onions, carrots, and celery with minced garlic in olive oil until soft.
This should take about 10 minutes over medium heat.
Add the ground beef and pork to the pot.
Cook until browned, breaking up the meat with a spoon.
This ensures that the meat is well incorporated.
Pour in the wine and allow it to simmer until reduced by half.
Stir in the crushed tomatoes, tomato paste, and milk.
Let it simmer on low heat for about 1.5 hours.
Prepare the Béchamel sauce by melting butter in a saucepan over medium heat.
Whisk in the flour until smooth.
Gradually whisk in the milk, stirring constantly until thickened.
Add nutmeg and set aside.
Preheat the oven to 375°F.
Layer the cooked ragu, Béchamel sauce, and lasagna sheets in a baking dish.
Top it all with Parmesan cheese and bake for about 45 minutes until bubbly and golden.