In a large pot or Dutch oven, brown the ground beef over medium-high heat. Drain off any excess grease.

Add the chopped onion and cook until softened, about 5 minutes. Stir in the minced garlic and cook for another minute until fragrant.

Stir in the crushed tomatoes, tomato paste, beef broth, oregano, basil, and red pepper flakes. Season with salt and black pepper to taste.

Bring to a simmer, then reduce heat to low, cover, and cook for at least 30 minutes, stirring occasionally. For a richer flavor, simmer for up to 1 hour.

In a medium saucepan, melt the butter over medium heat. Whisk in the flour and cook for 1-2 minutes, stirring constantly, to form a roux.

Gradually whisk in the warmed milk until smooth. Bring to a simmer, stirring constantly, until the sauce thickens.

Season with nutmeg, salt, and white pepper to taste. Remove from heat.

Preheat your oven to 375°F (190°C).

Spread a thin layer of meat sauce on the bottom of a 9x13 inch baking dish.

Arrange a layer of cooked lasagna noodles over the sauce. (You may need to break noodles to fit.)

Spread one-third of the remaining meat sauce over the noodles.

Spoon one-third of the béchamel sauce over the meat sauce.

Sprinkle with about one-third of the mozzarella and Parmesan cheeses.

Repeat the layers twice more: noodles, meat sauce, béchamel sauce, cheeses.

For the top layer, place noodles, spread the remaining béchamel sauce, and top with the remaining mozzarella and Parmesan cheeses.

Cover the baking dish with aluminum foil.

Bake for 25 minutes.

Remove the foil and bake for an additional 25-30 minutes, or until the cheese is golden brown and bubbly.

Let the lasagna rest for 10-15 minutes before slicing and serving.