Drain the clams and set aside on a paper towel. Heat the oil in
a skillet
and saute the scallions, parsley, capers, and mushrooms over medium
heat
for about 5 minutes. Remove from the stove and stir in the lemon
juice
and the cracker crumbs. Mash the egg half, both the white and
the yolk,
and stir it into the saute mixture along with the clams. Season
to taste
with salt and pepper. Lightly grease 4 scallop shells, and fill
with the
clam mixture. Heat for 4 or 5 minutes in a preheated 400-degree
oven, and
serve immediately.