actually healthy apple muffins

I generally try to avoid posting similar recipes too close to each other, but even though the last post was cupcakes, I promise these are different. Because they're Healthy! No, really! They are (relatively) low fat and they have lots of lovely bits of apple in them. And they're not too sweet. Muffins should not be monstrosities that are, as Jim Gaffigan says, just bald cupcakes. Eat them warm out of the oven while the tops are still crispy.

whole wheat apple muffins adapted from King Arthur Flour - makes 12

1 cup (4 oz) whole wheat flour (I've substituted 1/4 cup of ground flaxseed to up the fiber)
1 cup (4 1/4 oz) all purpose flour
1 teaspoon baking powder
1 teaspoon baking soda
1/4 teaspoon salt
1 tablespoon cinnamon
1 stick (4 oz) room temp butter (I've used 4oz oil)
1/2 cup (3 1/2 oz) granulated sugar
3/4 cup (5 5/8 oz) dark brown sugar, divided
1 large egg, lightly beaten
1 cup (8 ounces) buttermilk/ plain yogurt
2 large apples, peeled, cored, and coarsely chopped
1/4 cup shredded carrot, optional

Preheat the oven to 375°F. Spray a 12-cup muffin tin, or line with papers.

Cream the butter (or just mix in the oil) with the sugar and 1/4 cup dark brown sugar until fluffy. Add the egg and mix well, scraping bowl as needed. Mix in the buttermilk gently. (If you over-mix, the buttermilk will cause the mixture to curdle.) Pour in the dry ingredients and stir in with apples. Don't overmix!

Divide the batter evenly among the prepared muffin cups, sprinkling the remaining 1/2 cup brown sugar on top. Bake for 25 to 30 minutes, or until a toothpick inserted into the center of a muffin comes out clean. Remove from the oven, cool the muffins for 5 minutes in the tin, then turn them out onto a rack to finish cooling completely.