Saute onion & mushrooms in butter
Stir in lemon juice & Worcestershire or soy sauce and Simmer for 15 minutes
Drain mixture well (see note below)
Stir together with cheese and Salt & pepper and pour into pie
Put lattice strips of crust on top and brush with 1 beaten egg yolk
mixed with 1 Tbls water.
Bake 40 minutes at 350 degrees or until golden.
NOTE: The mushrooms produce quite a bit of liquid which is drained off before filling pie. I like to save this flavorful
juice as a starter for soup or pasta sauce. It is really tasty!