Mix and Match Muffins

3 cups unbleached flour
1/2 cup whole wheat flour
4 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
1 cup sugar, brown sugar, or sucanat
1/2 cup oil
1 cup milk
1/2 cup plain yogurt
2 eggs
Mixins: 1 teaspoon extract, 1 1/2 cups any combination of fruit*, chopped nuts, chocolate
*Possible fruit to use: mashed bananas, blueberries, finely chopped apples, raspberries, coarsely chopped cranberries
Preheat oven to 350 °. Line muffin tin with papers or spray with nonstick cooking spray. In large mixing bowl, combine, flours, baking powder, baking soda, salt, and sugar. (If preparing as a mix, simply combine all these ingredients in a ziptop bag, label well, mark with the wet ingredients and baking instructions.)
In a separate bowl, combine oil, milk, yogurt, and eggs. Whisk to blend. Add wet ingredients to dry. Fold gently until mostly moistened, but still lumpy. Fold in mix-ins.
For 12 large muffins, fill muffin cups completely, even mounding past their tops. For 18 kid-size muffin, fill almost full. Bake 25 – 35 minutes, depending on how much you fill them.