Preheat oven to 350 degrees
Heat the milk so that it is warm
Combine the milk and oats together in a bowl and allow to stand for about 15 minutes
Stir in the egg, brown sugar, and cooled butter and oil into the milk and oats mixture
In another bowl combine the flour, baking powder, cinnamon, and salt using a whisk
Slowly pour the wet mixture into the dry mixture using a whisk
Stir until just combined
Fold in the shredded apple with a spatula until evenly mixed in
Spray a muffin tin with cooking spray so that it evenly coats each cup; this spray makes it so that you don’t have to use liners and the muffins will come out of the tins without a problem
Fill each cup of the 12 cup muffin tin
Mix together the ingredients for the topping
Sprinkle each muffin with the topping mixture
Bake for 20-25 minutes or until the tops of the muffins spring back when lightly touched and a toothpick comes out clean when inserted
Allow to cool completely
Store in an airtight container for 2-3 days