Luncheon Mushrooms in Sour Cream

2 pounds fresh mushrooms
1 bunch scallions, chopped
1/2 cup butter
Juice of 1/2 lemon
2 teaspoons salt
Dash of white pepper
Dash of ground nutmeg
1 (8 ounce) container sour cream
3 tablespoons sherry or white wine (optional)
3 English muffins, split, or 6 frozen puff patty shells
Parsley sprigs

Rinse, pat dry and slice thinly the mushrooms. Saut