Preheat oven to 375°F (190°C).
In a large fry pan, melt 2 tbsp (30 ml) of the butter. Add mushrooms and cook over medium-high heat until tender. Drain. Stir together mushrooms and 1 cup (250 ml) of the tomato sauce; set aside.
To make the béchamel sauce, melt remaining butter in a small saucepan; add flour, stirring to blend well. Add milk, nutmeg and salt and cook over medium heat, stirring until thickened. Remove from heat; set aside.
In a bowl, stir together Canadian Ricotta, basil, 1 cup (250 ml) of the Canadian Mozzarella, 1/4 cup (50 ml) of the Canadian Parmesan cheese and 1 cup (250 ml) of the béchamel sauce.
To assemble, spread 1 cup (250 ml) of the remaining tomato sauce in the bottom of a 13′ x 9′ (33 x 23 cm) lasagna dish. Arrange a layer of 5 or 6 noodles over sauce, overlapping slightly to the pan edges.
Spread ricotta mixture evenly over noodles and repeat with another layer of noodles. Top with mushroom layer and last layer of lasagna noodles. Spread with remaining tomato sauce, covering the noodles completely, and drizzle with béchamel sauce. Top with remaining mozzarella and Canadian Parmesan.
Cover with foil and bake for 35 minutes or until noodles are tender. Remove foil and bake for an additional 10 minutes or until golden.