1. Place loaves in a bowl. Cover bowl with plastic wrap and let rise until doubled, 45 minutes to 1 hour.
2. Punch dough down, knead loaves together in bowl, and shape into a ball.
3. Transfer ball to an oiled 12- by 15-inch baking sheet. With oiled hands or a lightly floured rolling pin, flatten ball into an 11- by 13-inch oval. Cut out eyes, nose, and mouth; openings should be at least 1 1/2 to 2 inches wide. (To make small loaves, divide dough into 4 equal pieces, roll into 4- by 6-in. ovals; eye, nose, and mouth openings should be at least 1 to 1 1/2 in. wide.) Lift out cutout dough and bake on another pan or use for decorations.
4. Cover shaped dough lightly with plastic wrap and let rise until puffy, about 20 minutes.
5. Mix egg with milk; brush over dough.
6. Bake in a 350° oven until well-browned, 30 to 35 minutes. Cool on a rack. Serve warm or cool.