whole wheat apple muffins

I am a muffin person. I know that there's been a recent uprising for the love and adoration of cupcakes but when it comes down to it, muffins are my first love. I found this recipe on Smitten Kitchen a little more than a year ago while I was a baker in my campus coffee shop and ever since I've tried it, the recipe has never let me down.

whole wheat apple muffins

1 cup whole wheat flour
1 cup all-purpose flour
1 teaspoon baking powder
1 teaspoon baking soda
1/4 teaspoon salt
1 tablespoon cinnamon
1/2 cup (1 stick) unsalted butter
1/2 granulated sugar
1/2 brown sugar
1 large egg
1 cup buttermilk or yogurt
2 large apples peeled, cored, and coarsely chopped

Preheat oven to 450 degrees. Combine flours, baking powder, baking soda, salt, and cinnamon in a bowl and set aside. In a separate bowl, cream butter then add granulated sugar and 1/4 cup of brown sugar. Add egg and mix until combined. Slowly add buttermilk* but be careful not to over-mix so that the buttermilk does not curdle. Add flour mixture. Fold in apples. Divide into muffin cups and sprinkle the remaining brown sugar on top.** Bake for 10 minutes at 450 degrees and then for 5-10 at 400 degrees until golden brown.

Eat. Fall in love.

*I've tried this with buttermilk and yogurt and both work perfectly (yogurt is cheaper)
**I used a little brown sugar and granulated sugar.