Heat oven to 400°F. Shape dough into 24 balls, using about 1 Tbsp. dough for each ball. Flatten each to 4-inch round. Spoon about 1 heaping Tbsp. chicken mixture onto centre of each round. Brush edges evenly with half the egg; fold in half. Seal edges with fork; place on parchment-covered baking sheet. Brush with remaining egg.