1 ½cuppeeled and chopped apples(215g) I prefer my apple pieces chopped smaller rather than larger. You can use your preferred apple, I like to use a sweet/tart kind like Golden delicious or Gala.
Preheat oven to 375 F (190C) and line a 12-count muffin tin with paper liners (or grease and flour).
Prepare the crumble first by whisking together flour, sugars and cinnamon.
Pour the melted butter into the mixture and, using a fork, stir until crumbles form. Set aside.
In medium-large bowl, whisk together oil, brown sugar, granulated sugar, and buttermilk. Whisk well until all ingredients are well combined (about 1 minute).
Add eggs, whisking until combined.
Stir in vanilla extract.
In separate, medium-sized bowl, stir together flour, baking powder, cinnamon and salt.
Gradually stir flour mixture into wet mixture until just combined (do not over-mix!).
Gently fold in apple pieces.
Divide batter into prepared muffin tins (filling each about ¾ of the way full).
Top with crumble topping, splitting evenly among muffins.
Bake on 375F (190C) for 25 minutes (toothpick inserted in center should come out mostly clean with no wet batter on it).
Allow muffins to cool before eating.
*Please note that this crumble recipe makes a lot of crumble -- as much as you see in the photos. I use all of it when I make these muffins because I like a lot of streusel, if you don't like a lot of streusel, please halve the crumble.