Sift together the flour, sugar, salt, and baking powder; stir in whole-wheat flour.
Combine egg, milk, and butter.
Make a well in dry ingredients and add liquid all at once.
Stir just till moistened.
Fill greased muffin pans 2/3 full.
Bake in hot oven (425°) 15 to 18 minutes or till done.
Makes about 10 muffins.