In a medium sized bowl, add the flour, sugar, brown sugar, salt, and rolled oats.  Mix until evenly combined.

Add the butter to the oat mixture.  Using a pastry cutter or fork, mix the butter into the oat mixture until it’s the texture of coarse sand and you can no longer see chunks of butter.

Set in the fridge until ready to use.

Preheat your oven to 350° F and place muffin liners in a twelve-count muffin tin.

In a medium sized bowl, mix the flour, cinnamon, baking powder, baking soda, and salt until evenly combined.

In a separate, larger bowl add the butter, sugar, and applesauce. Whisk until well combined and the sugar is fully incorporated into the butter.

Add the vanilla and eggs to the butter mixture, whisking until completely combined.

Pour the dry ingredients into the wet ingredients, stirring to combine. Once the dry ingredients are almost completely mixed in, add the apples.  Give the mixture a few more stirs, incorporating the apples evenly.

Scoop the batter evenly into the muffin liners.  Take the crumble mixture out of the fridge and sprinkle across the top of each, lightly pushing the crumble into the muffin batter if needed.

Bake muffins for 20-23 minutes, until a toothpick stuck in the center of a muffin comes out clean.

Let cool on a cooling rack for at least 15 minutes and then remove from the tin.  These muffins are best eaten the same day, but can be saved for 1 to 2 days in an airtight container.