Coat the bottom of a large skillet with the olive oil and place over medium heat. Remove turkey sausage from the casings by slicing through one side with a sharp knife. Discard casings and place turkey sausage in heated skillet. Cook and stir, breaking up the sausage, until no longer pink. Drain as much grease from the pan as possible and return pan to heat and add garlic. Season with salt and fresh ground pepper, to taste. Cook and stir for another minute or two and then remove the pan from the heat and set aside.
In a small mixing bowl, combine ricotta, egg, salt,and chopped basil. Set aside.
Coarsely chop mushrooms and set aside.
Lightly coat the bottom of a deep freezer safe 13" x 9" pan with marinara sauce. Place 4 lasagna sheets over the sauce, slightly overlapping to fit pan. Spoon 1/3 of ricotta mixture over the lasagna sheets and spread out evenly with a knife. Sprinkle 1/3 of cooked turkey sausage over the ricotta. Top with 1/3 of chopped mushrooms, purposely allowing some to fill in edges of pan around the lasagna. Sprinkle with 1/4 of both the mozzarella and Parmesan and then pour a scant amount of marinara over the top.
Layer as above for a total of 3 more layers.
Top with remaining 4 lasagna sheets and top with a good amount of marinara sauce. Use a knife or spatula to smooth out the sauce to the edges of the pasta sheets. Sprinkle with remaining mozzarella and Parmesan.
Generously coat the bottom of a large piece of heavy duty foil with non-stick cooking spray. Cover the lasagna with the foil, crimping edges of foil around the pan. Wrap the covered pan completely in one or two more sheets of foil.
Place pan in freezer.
Defrost completely in refrigerator overnight or follow directions below for transport.
Preheat oven to 375 degrees F. Bake covered lasagna for 50 minutes. Remove foil and continue to bake another 10 to 15 minutes until heated through and bubbly around edges.