Preparation

• In a Dutch oven, heat 1 Tbs. olive oil and the pancetta over medium heat, stirring, until the pancetta is lightly browned, about 5 minutes. Add the onion, carrot, celery, garlic, and oregano and cook, stirring, until the veggies are softened, about 5 minutes; push to the side of the pan. Increase the heat to medium-high. Add the remaining 1 Tbs. olive oil to the center of the pan and crumble in the ground beef; cook without stirring for 3 minutes. Break up the meat with a spoon, and continue to cook, stirring occasionally, until well browned, about 3 minutes.
• Add the tomatoes and 1 cup water to the pot; simmer, stirring occasionally, until thickened, about 30 minutesS. eason with salt and pepper. Remove from the heat.
• Meanwhile, bring a large pot of well-salted water to a boil. In a medium saucepan, melt the butter over medium heat. Add the flour and cook, whisking constantly, for 1 minute. Whisk in the milk in a steady stream and simmer for 2 minutes, whisking until it thickens. Remove from the heat, stir in 1 cup Parmigiano and season with salt and pepper. Let cool, stirring occasionally to prevent a skin from forming.
• Cook the lasagna noodles in the boiling water until al dente, about 10 minutes. Drain and transfer to a bowl of cold water.
• Preheat the oven to 400°F. Coat a 9-by-13-inch baking dish with nonstick cooking spray. Spread 3/4 of the cup meat sauce over the bottom of the dish to coat. Add a layer of noodles, overlapping slightly. Top with 1 cup of the meat sauce, then a layer of noodles; add 1 cup of the bechamel sauce, spreading to coat. Repeat the layers. Add a fifth layer of noodles and top with the remaining meat sauce; dollop with the remaining bechamel. Cover with greased parchment, then wrap the pan with foil. Bake for 1 hour; uncover and sprinkle with the remaining 1/4 cup Parmigiano. Bake for 15 minutes more. Loosely cover again with the foil and let stand for 30 minutes before slicing.