2/3 cup milk
1 egg, beaten
2 tsp lemon juice
1 tsp orange juice
1 tsp grated lemon peel
1 tsp grated orange peel
Preheat oven to 425 degrees. Spray 12 muffin cups with nonstick cooking spray; set aside.
In a medium bowl combine the milk, egg, lemon juice, orange juice, lemon peel and orange peel. Stir together to blend then add the muffin mix; stir together just until moistened. Fill the prepared muffin cups about 2/3 full each. Bake 12 to 16 minutes or until a wooden toothpick inserted in the center comes out clean. Cool in the pan about 2 to 3 minutes then add the glaze to the warm muffins.
Glaze: Mix together 1/2 cup powdered sugar and 1 tablespoon of lemon or orange juice. Drizzle over the warm muffins.