Heat olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat. Add ground beef and pork, breaking it up with a spoon. Cook until browned, about 8-10 minutes. Drain off excess fat.

Add chopped onion, carrots, and celery to the pot. Sauté until vegetables are softened, about 8-10 minutes. Stir in minced garlic and cook for another minute until fragrant.

Pour in the red wine, scraping the bottom of the pot to deglaze. Let it simmer until almost completely evaporated, about 5 minutes.

Stir in the crushed tomatoes, diced tomatoes, tomato paste, beef broth, milk, bay leaf, and dried oregano. Bring the sauce to a gentle simmer. Reduce heat to low, cover partially, and let the Bolognese simmer for at least 2.5 hours, or up to 3 hours, stirring occasionally. The longer it simmers, the richer the flavor. Season with salt and pepper to taste. Remove the bay leaf before assembly.

While the Bolognese simmers, melt butter in a medium saucepan over medium heat. Add flour and whisk constantly for 1-2 minutes to form a roux, cooking out the raw flour taste.

Gradually whisk in the warm milk, a little at a time, ensuring no lumps form. Continue whisking until the sauce thickens to a creamy consistency, about 5-7 minutes.

Remove from heat and stir in salt, white pepper, and nutmeg. Keep warm or cover to prevent a skin from forming.

If using traditional lasagna noodles, cook them according to package directions until al dente. Drain, rinse with cold water, and lay flat on parchment paper or a clean kitchen towel to prevent sticking. No-boil noodles do not require this step.

Preheat oven to 375°F (190°C). Spread a thin layer of Bolognese sauce (about 1/2 cup) on the bottom of a 9x13 inch baking dish.

Place a layer of lasagna noodles (3-4 noodles, depending on their size) over the sauce, slightly overlapping if necessary. Spoon about 1.5 cups of Bolognese sauce evenly over the noodles. Drizzle about 1 cup of béchamel sauce over the Bolognese. Sprinkle generously with Parmesan cheese (about 1/4 cup).

Repeat the layers: noodles, Bolognese, béchamel, Parmesan. You should get 3-4 layers. For the final layer, place noodles, then the remaining béchamel sauce, and a generous sprinkle of Parmesan cheese. If desired, add 1/2 cup shredded mozzarella cheese on top for an extra cheesy crust.

Cover the baking dish tightly with aluminum foil. Bake for 30 minutes.

Remove the foil and continue baking for another 30-45 minutes, or until the top is golden brown and bubbly. If the top browns too quickly, you can loosely tent it with foil again.

Let the lasagna rest for at least 15-20 minutes before slicing and serving. This allows the layers to set and prevents it from falling apart.