Instructions:
- Sauté Soffritto: Heat olive oil in a large Dutch oven over medium heat. Add onion, carrot, and celery. Cook gently until softened, about 8–10 minutes. Add garlic; cook 1 minute more until fragrant.
- Brown Meat: Increase heat to medium-high. Add ground beef and pork. Break up meat and cook until fully browned. Drain off excess fat.
- Deglaze: Pour in the red wine. Scrape up any browned bits from the bottom of the pot. Let the wine reduce by half.
- Simmer Ragu: Stir in crushed tomatoes, diced tomatoes, stock, oregano, and pepper flakes. Season generously with salt and pepper. Bring to a simmer, then reduce heat to the lowest setting, cover partially, and cook for a minimum of 2.5 hours, stirring occasionally, until thick and rich.
- Make the Roux: While ragu simmers, melt butter in a saucepan over medium heat. Whisk in the flour briskly and cook for 1–2 minutes to create a white roux.
- Finish Béchamel: Gradually whisk in the warm milk. Bring the mixture to a simmer, whisking constantly, until the sauce thickens enough to coat the back of a spoon (about 5–8 minutes). Season with salt and nutmeg. Remove from heat.
- Prepare Ricotta Filling: In a bowl, mix ricotta, beaten egg, 1/2 cup Parmesan, and parsley. Season lightly.
- Assembly Prep: Preheat oven to 375°F (190°C). Grease the 9x13 inch dish. Spread a thin layer of Ragu on the bottom.
- Layer 1: Place pasta sheets over the ragu. Top with one-third of the Ricotta Mixture (dolloped), one-quarter of the Ragu Sauce, one-quarter of the Béchamel Sauce, and one-third of the Mozzarella Cheese.
- Repeat: Repeat the layering sequence (Pasta, Ricotta, Ragu, Béchamel, Mozzarella) two more times.
- Top Layer: Finish with a final layer of pasta sheets, the remaining Béchamel, and the remaining Mozzarella and extra Parmesan.
- Bake: Cover the dish tightly with foil. Bake for 30 minutes. Remove foil and bake for another 15–20 minutes until the top is bubbly and golden brown.
- Rest: Let the lasagna rest on the counter for a crucial 15 minutes before slicing and serving to allow the layers to set.