Spinach, thoroughly thawed but not cooked and thoroughly squeezed dry (3 minutes on high in the microwave thaws it perfectly).
Cook the scallions slowly in the butter until limp but not browned. Remove from heat. Add spinach and, if necessary, stir over moderate heat for a minute to evaporate all its water (this won't be necessary if it was thoroughly squeezed dry in a strainer). Stir in salt, pepper and nutmeg; taste carefully for seasoning.
In a mixing bowl beat eggs and add cream. Then add spinach and mushrooms; stir well. Have this ready when partially baked pastry shell is coming out of the oven. Pour mixture into hot shell. Gently stir spinach and mushrooms around with a fork to distribute evenly. Sprinkle cheese over top. Bake at 375 degrees for 25-30 minutes. Quiche is done when inserted knife comes out clean.