Apple Streusel Muffins

For the streusel:

Combine all streusel ingredients in a small mixing bowl. Mix together using your hands, squeezing the butter pieces in between your fingers and forming small clumps. Set aside.

For the muffins:

Preheat oven to 375 and spray muffin tin lightly with vegetable oil cooking spray.

In a large mixing bowl, use a whisk to mix together flour, whole wheat flour, brown sugar, baking powder, baking soda, cinnamon, and salt.

In a small mixing bowl, whisk together eggs, vegetable oil, sour cream, milk, and vanilla extract. Whisk until smooth.

Pour the wet ingredients into the large mixing bowl with the dry ingredients. Using a rubber spatula, gently mix the batter until just combined—it’s ok if a few streaks of flour remain, don't overmix! Add the diced apples to the batter.

Fill the greased muffin tin with the batter--each cup should be about ¾ full. Top each of the muffin cups evenly with the streusel topping, lightly pressing down to make sure the topping sticks to the muffins.

Bake the muffins for about 20 minutes, or until a toothpick inserted into one of the muffins comes out clean. Serve warm or let cool before serving.