Start by whipping up the white sauce. First, take the butter, and melt it in a large saucepan. Then stir in the flour to make a paste, and add the milk. Continue to stir until this mixture begins to thicken. Add the Parmesan cheese and ricotta. Remove from heat, and set aside.
2
Stacking the Lasagna
Start by preheating the oven to 350. Then put a little sauce on the bottom of the pan, and cover it with a layer of noodles. Spread the veggie mixture, more sauce and a layer of mozzarella cheese. Repeat until you get to the top layer of the lasagna. Then spread the last layer of sauce, and load up with the rest of the mozzarella cheese. Sprinkle grated parmesan over it.
3
Finally, cover the lasagna with aluminum foil, and bake for about 30 minutes. Remove foil and bake until cheese is brown.