Preheat oven to 350 degrees. Cook lasagna noodles according to package directions. Cook in large bowl of cold water; set aside. Saute onions in 2 tablespoons butter until tender, about 5 minutes. Combine spinach, onions, Mozzarella cheese, sour cream and egg; set aside.
Melt 1/4 cup butter in a saucepan, stir in flour, instant bouillon and pepper. Stir in milk and cream. Bring to boil, stirring constantly. Boil and stir 1 minute. Remove noodles from water. Pat dry with paper towels. Spread about 1/4 cup spinach mixture over each noodle. Roll up jelly roll fashion starting at short end. Spread a small amount of sauce on bottom of buttered 2 quart rectangular baking dish. Place rolls in dish. Spoon remaining sauce over roll ups. Sprinkle with Parmesan cheese. Bake 30 to 35 minutes or until hot and bubbly.
