Preheat the oven to 375°. Line a 12-cup muffin tin with muffin papers or spray with nonstick cooking spray.
In a large mixing bowl, combine the flours, baking powder, baking soda, salt, and sugar.
In a separate bowl, combine the oil, milk, yogurt, eggs, and extract, if using. Whisk to blend.
Add the wet ingredients to the dry. Fold gently until mostly moistened, but still lumpy. Fold in mix-ins of your choosing.
For 12 large muffins, fill muffin cups completely, even mounding past their tops. For 18 kid-size muffins, fill almost full.
Bake 25 - 35 minutes, depending on how much you fill them. Bake until a tester comes out clean. Cool on a wire rack before serving.
Nutritional values are approximate, and do not include any mix-ins you might choose.To freeze: baked and cooled muffins can be stored in an ziptop freezer bag in the freezer for up to 6 weeks.To make as a mix: Take a large ziptop bag or container and label it with the wet ingredients and the baking instructions. Measure out the dry ingredients into the bag. Seal and store until ready to use.