Heat a large saute pan over medium-high heat. Add the olive oil, pancetta and onions and cook, stirring until the onion softens and starts to brown (about 4 mins). Add the mushrooms (pan will be crowded to start). Cook, stirring every 2 or 3 minutes, until the mushrooms have released their water. Add the white wine and raise heat to high. Cook, stirring, until almost all of the liquid had evaporated (about 8 mins). Add salt & pepper as needed. Remove from heat and set aside.
Heat the milk and set aside. In a heavy 2 to 3 quart saucepan, melt the butter over moderate heat, then stir in the flour. Stirring continuously, cook over medium heat for 2 ro 3 minutes untl the paste begins to thin out. Add the warm milk in a steady stream while whisking the mixture, to make bechamel sauce. Add nutmeg to taste. Bring to a boil. Reduce heat to low and let simmer about 10 minutes, strring every few minutes. The sauce should coat the back of a spoon, if it is too thick, add a little more milk. Remove from the heat and cover the surface with plastic wrap until assembling the lasagna to keep a skin from forming.
In a separate bowl, combine the smoked and regular mozzarella. Using a 13x9-in pan, spoon a few tablespoons of the bechamel sauce over the bottom. Cover with a layer of lasagna sheets. Spread on half of the mushroom mixture, then a third of the bechamel, then a thrid of the mozzarella. Repeat the layers, ending with a final layer of lasagna sheets. Spread what remains of the bechamel evenly over the lasagna and sprinkle with the remaining mozzarella.
At this point, the lasagna may be refrigerated and baked later. Bake covered at 375 degrees F for 45 minutes, remove the foil and bake an addtional 15 minutes until golden brown. Let stand for 10 minutes before serving.