Preheat oven to 350 degrees. In a sauté pan over medium-high heat, sauté the sausage, breaking it up into small pieces, until browned. Drain any fat from the pan and set aside.
In a bowl, stir together the ricotta, milk, egg and ¾ cup parmesan.
In a 9x13 baking dish, spread 1 cup tomato sauce. Cover with a single layer of noodles without overlapping them. Spread on a third of the ricotta mixture, another cup of the sauce and top with a third of the sautéed sausage. Add two more layers of noodles, ricotta, sauce and sausage. Top with a final layer of noodles, remaining sauce, the mozzarella and the remaining 1/4 cup of Parmesan. Be sure the top layer of noodles is fully covered with sauce (if any edges are peeking out uncovered, they will be crispy instead of soft).
Bake uncovered for 45-50 minutes in the middle of the oven, until bubbly and golden brown on the edges. If the cheese starts to get too brown, cover the pan with foil during baking. Let stand for 5 minutes before cutting.
Note: Lasagna can be assembled and frozen before baking. Place in refrigerator the night before you plan to bake.