Place bran cereal in a large bowl.  Pour boiling water over the bran and stir.  Add the buttermilk and stir till well blended.

Cream butter and sugar with mixer.  Add eggs.  Mix well.   Add the bran/buttemilk mixture.  Mix well.  Add the dry ingredients.  Mix well.  Store in the refrigerator in a covered container.  May be stored for several weeks.

Fill muffin cups two thirds full.  Bake at 375 degrees for 22 minutes.