Preheat the oven to 220 C (425 F) and grease or line a 12 muffin tray with muffin liners.
First, peel and chop the apples into small cubes. Place them in a bowl with the flour and cinnamon and coat them. Place aside.
In a medium bowl add the oil, milk, vanilla, and eggs and mix together.
In a large bowl add the sugar, brown sugar, flour and baking powder and cinnamon. Fold through the wet ingredients until just combined.
Lightly fold through the apples and then scoop into the muffin cases. The mixture should fill the cases up about ⅔.
Crumb Topping;
Add the flour, brown sugar and cinnamon into a small bowl and mix through the melted butter.
Top each muffin with a sprinkle of the crumb topping and then place in the oven for 15-20 minutes or until a skewer inserted into the middle comes out clean.