Combine the almonds, pecans, and pistachios in a food processor fitted with the "S" blade. Pulse until all of the nuts are broken down and are similar in size. Set aside.
Make the muffins
Preheat oven to 350° F. Line a muffin pan with liners, set aside.
In a large bowl, whisk together the flours, cornstarch, oats, cinnamon, baking powder, xanthin gum, baking soda, and salt; set aside.
In a medium bowl whisk together the eggs and Pyure Organic Stevia. Add the melted butter, buttermilk, vanilla and applesauce, whisk to combine.
Add the wet ingredients to the dry ingredients and whisk just until no lumps remain. Fold in the shredded apple.
Use an ice cream scoop to evenly scoop batter into the prepared muffin cups. Scoop 1/2 tablespoon of the ginger nut crumble over each of the muffins.
Bake for 20 minutes until a toothpick inserted near the center comes out clean. Remove and cool in the pan for 5 minutes. Transfer to a wire rack and cool completely.