In a small bowl, mix together the topping ingredients and set aside.

In a medium bowl, whisk together the flours, baking soda, salt and cinnamon.

In a large bowl, combine the ¾ c. brown sugar, and oil, applesauce and vanilla until combined; add the eggs, one at a time, mixing well after each addition.

Add the flour mixture in 2 batches, alternating with the buttermilk. Mix just until combined.

Gently stir in the apple chunks.

Spoon into greased or paper lined muffin cups until 2/3 full and sprinkle with the topping mixture.

Bake at 400 degrees for about 15-20 minutes depending on the size of your pan.

Let cool on wire rack for 10 minutes, remove from pan and cool completely on wire rack.