All-Purpose Muffins

I love a recipe like this one, that can be varied in infinite ways. Here the basic muffin batter can be altered to make a dozen different types of easy-to-prepare muffins. Thanks to my dear friend Cara Tannenbaum for sharing her recipe. The recipe that follows is the basis for making muffins with the flavourings and other enhancements listed in the variations below it; this recipe is not meant to be made as is.