Preheat the oven to 350 degrees F. Spray 9 cavities of a muffin tin and lightly flour. Do not use muffin liners and these muffins will stir to them. Set aside.
In a large bowl, pour in the flour Remove 1 tablespoon of the flour ad return it to the flour container. Add in the cornstarch, baking soda, salt, and cinnamon. Mix until combined.
In another bowl, mix together a large egg, Greek yogurt ( I use apple cinnamon in these muffins and love it! Plain or vanilla will also work. Full fat or 1% for best results -- fat free tends to be a bit watery), coconut oil (measured when melted), vanilla extract, and brown sugar. (If you are used to healthier muffins/snacks 1/3 cup brown sugar should be great for you and If not I would recommend doing 1/2 cup). Mix until well Combined.
Peel ad finely chop the apple. Toss with the moon juice and discard any extra lemon juice that doesn't coat the apples. Toss with the flour mixture. (this is important to keep the apples dispersed evenly thought the muffins).
Mix the wet and dry ingredients until JUST combined. Over-mixing yields denser muffins.
Fill up 9 muffin cavities evenly with the mixture -- each cavity will e a litle over 3/4ths of the way full.
In another bowl, toss together the flour, quick oats cinnamon, and brown sugar. Pour in the coconut oil (measure when melted) and mix to combine. Add a bit more coconut oil if too dry or a bit more flour if too wet.
Top each muffin evenly with this crisp topping.
Fill the empty cavities of the muffin tin with mater to ensure even baking.Bake for approx 30 minutes test with a toothpick to see if comes out clean.
