In frying pan, melt butter; add mushrooms and onion, stirring until all
liquid evaporates, about 5 minutes. Add seasonings and flour; stir until
blended. Gradually stir in milk and sherry. Blend in egg yolks one at a
time. In a separate bowl, beat egg whites until stiff peaks form. Fold
whites into mushroom mixture until just blended; fold in about 4/5 of
cheese. Spoon mixture into buttered individual souffle dishes or single
large souffle dish. Sprinkle remaining cheese on top. Bake small dishes
for 25-30 minutes at 375 degrees. Bake large souffle at 350 degrees for
35- 40 minutes or until puffy and golden. Serve immediately.
