Place pastry shells on a cookie or baking sheet, "tops" up. Separate one of the eggs. Beat egg yolk and brush over tops. Bake in preheated 400°F oven 20 to 24 minutes or until puffed and golden brown. Let stand 5 minutes. Remove "tops"; reserve for garnish. Pull out soft pastry from shells.
In a large bowl, beat together eggs, egg white, cream, chives, nutmeg, salt and pepper. Melt butter in a large skillet over medium-high heat. Add egg mixture; cook, stirring frequently, until eggs are soft set. Combine 1/4 cup Swiss and 1 cup Cheddar in a medium bowl; set aside. Stir remaining Swiss and Cheddar into egg mixture; cook, stirring constantly, just until the cheese melts.
Sprinkle 1 tablespoon reserved cheese mixture in bottom of each shell. Fill with egg mixture; top with remaining cheese mixture. Return to oven; bake 3 to 5 minutes or until cheese is melted . Garnish with "tops."