Chop onion cook it alone with Sausage & Mushrooms until done.
Drain grease and line this mixture in the bottom of the pie.
Beat eggs and cube swiss cheese. Add sour cream to eggs and beat well. Add Swiss cheeseto this mixture.Pour the egg, sour cream swiss cheese mixture on top.
Grate the cheddar cheese and sprinkle over the top of the whole pie.
Bake for about 35 min at 375