Butter two 11 x 7-inch baking dishes (or use 1 large casserole dish).
In a skillet melt butter over medium heat; add in onions and mushrooms and saute until softened (about 6-7 minutes) add in the garlic the last 2 minutes; remove from heat.
In a large mixing bowl combine the undiluted soup, half and half cream and alfredo sauce.
Add in the sauteed onion/mushroom mixture with cooked turkey or chicken and cooked spaghetti, peas, 1/2 cup Parmesan cheese and 1-1/2 cups Swiss cheese; mix well to combine and season with salt and pepper.
Transfer to the baking dishes or large casserole dish.
In a bowl mix together the crushed croutons with 3/4 cup grated parmesan cheese and pinch paprika; sprinkle evenly over the casserole.
Bake for about 30 minutes or until hot and bubbly.