In a medium saucepan, heat the butter over medium-low heat until melted. Add the flour and stir until smooth.
Over medium heat, cook until the mixture turns a light, golden sandy color, about 6 to 7 minutes.
Meanwhile, heat the milk in a separate pan until just about to boil.
Add the hot milk to the butter mixture 1 cup at a time, whisking continuously until very smooth. Bring to a boil.
Cook 10 minutes, stirring constantly, then remove from heat. Season with salt and nutmeg, and set aside until ready to use.
In a medium skillet, cook the pancetta. Add garlic. Add wine and cook for an additional 2 minutes. Stir in parsley and salt and pepper.
Preheat oven to 375 degrees. Butter an 18-by-13 1/2-by-3-inch baking dish. Spread a layer of béchamel sauce on the bottom of the dish. Add half the pasta to the pan. Top with half the remaining sauce and half the pancetta mixture.
Sprinkle with half of the Parmesan and pecorino. Top with remaining pasta.
Top with remaining pancetta mixture, sauce and cheeses. (Can be prepared one day in advance. Cover and refrigerate overnight. Let lasagna come to room temperature before baking.).
Cover with foil and bake for 50 to 60 minutes. Remove foil and bake for 10 to 15 minutes. Remove from the oven. Let rest 10 to 15 minutes before serving.
SMALLER VERSION (serves 6 to 8).
4 cups béchamel sauce (see recipe).
1/2 pound pancetta, diced.
2 garlic gloves, minced.
1/2 cup white wine.
1/4 cup chopped parsley.
1/2 cup grated Parmesan.
1/2 cup grated pecorino Romano.
Salt and pepper.
1 pound penne, slightly undercooked and drained.
Follow same directions as for larger version, except use a 13-by-9-by-3-inch baking dish with nonstick cooking spray.
Decrease baking time to 20 to 30 minutes, covered with foil, and an additional 10 to 15 minutes uncovered. Let rest 10 to 15 minutes before serving.
Per serving based on 25: 508 cal.; 32 g pro.; 55 g carb.; 16 g fat (9 sat., 5 monounsat., 2 polyunsat.); 58 mg chol.; 847 mg sod.; 2 g fiber; 8 g sugar; 29 percent calories from fat.