Preheat oven to 425°F (Unless making mini muffins, in which case preheat oven to 375°F). Spray muffin tin with cooking spray or line with cupcake liners. Set aside.

In a large bowl, toss together the flours, baking powder, salt, cinnamon and nutmeg until all is combined. Set aside.

In a separate medium bowl, whisk together the eggs and sugar until combined. then whisk in the milk, oil, and vanilla extract. Fold wet ingredients into the dry and mix everything together with a spatula or wooden spoon until just combined. Do not overmix. Fold in the peeled and diced apple chunks.

In a small bowl, mix your oat topping. Simply toss together the oats, remaining brown sugar and remaining ground cinnamon.

Spoon batter into the prepared muffin tins. Fill all the way to the top. Sprinkle the oat topping evenly over the muffin tops and press down gently with your fingers.

Bake muffins at 425°F for 5 minutes (Explanation below) then, keeping the muffins in the oven, lower the oven temperature to 375°F and continue to bake until tops are lightly golden and a toothpick inserted into the center comes out clean (See at bottom for cooking times depending on what size muffin tin you're using)

For jumbo muffins: 5 minutes at 425°F then 20-25 minutes at 375°F.

For standard size muffins: 5 minutes at 425°F then 14-16 minutes at 375°F.

For mini muffins: Preheat oven to 375°F to begin with and cook for 10-12 minutes at the same temperature the entire time.