Preheat oven to 400°. Rinse and dry mushrooms. Remove and finely chop the
stems; set aside. Coat mushroom caps in a mixture of oil, 2 teaspoons of the
lemon juice, salt and pepper. Arrange on a baking pan, stem side down, and
bake 5 minutes.
Remove stems from spinach, rinse and drain. Heat butter in a saucepan, add
onions, and cook till wilted. Add mushroom stems and 1 teaspoon lemon juice.
Cook briefly, stirring. Add spinach and cook till most of the liquid is
evaporated. Add cream, nutmeg, salt and pepper; stir. Add the egg and cook
about 10 seconds. Purie the mixture in a blender or food processor, return
to the pan and add ham. Fill mushroom caps and sprinkle with cheese. Bake
for ten to fifteen minutes.
