In a skillet over medium low heat, melt butter; brown bread cubes. Remove from skillet and set aside. Sauté mushrooms in butter for about 7 to 10 minutes. In a buttered 1-1/2quart casserole dish, alternate layers of bread cubes, mushrooms, shrimp, and cheese.
Combine eggs, milk, and seasonings; pour over layers. Place casserole dish in a pan of hot water and bake at 350° for about 1 hour and 15 minutes, or until set.