Crumble and cook beef in 10- to 12-inch frying pan over medium heat until well browned, about 5 minutes.
Add onion, garlic, and mushrooms and cook for about 10 minutes more or until onion is soft. Stir in soy, scraping to loosen brown bits. Remove from heat. Stir in eggs and pepper. Cool.
On a lightly floured board, roll each shell out to a 7-inch circle. Spoon 1/6 (about 1/2 cup) of meat mixture onto center. Moisten edges with egg white and with seam on top, pinch firmly to seal. Flute edge. Pierce tops in several places to allow steam to escape
Set on ungreased baking sheet. If made ahead, cover and chill up to 8 hours. . Bake, uncovered, at 450 degrees for about 20 minutes or until golden. Serve warm. Makes approximately 6 servings.
A slice of cheddar cheese may also be added to pastries.