Heat oven to 375°F. Separate dough into 8 biscuits. Press or roll each biscuit to form 5-inch round.
Spread each biscuit round with about 1 teaspoon mustard. Place 1 oz. corned beef, 1 tablespoon sauerkraut and 1 tablespoon cheese in center of each round. Fold in half; seal edges. Prick top with fork to allow steam to escape. Place on ungreased cookie sheet. Brush tops with egg.
Bake at 375°F. for 13 to 16 minutes or until golden brown.