Preheat oven to 200C (425F). Line a muffin tin with paper liners and set aside.

Make wet batter: In a mixing bowl crack in the eggs, add brown sugar and mix for 1-2 minutes until combined, add in vanilla extract and butter milk and whisk to combine. Add in a butter and stir until it dissolves. Add in flour, baking powder, baking soda, cinnamon, salt and a smooth batter forms.

Make dry batter: In a separate bowl combine dry ingredients, all purpose flour, salt, cinnamon, brown sugar. In the baking process, this will coat your apples. Mix well.

Add diced apples to the dry mixture, add the butter to the space and mix until completely coated.

Add dry mixture to the wet batter, add apples, fold gently with a spatula, do not over mix. Do not over mix at this point. Leave the batter chunky, this will create a better texture.

Meanwhile prepare the caramelized apples. In a non-stick small pan, add butter, sugar, apple, cinnamon, salt and cinnamon. Cook for 4-5 minutes until caramelized and apples are tender.

Make crumb topping by mixing melted butter, cinnamon, all purpose flour, cinnamon, sugar and brown sugar.

Make vanilla icing by mixing powdered sugar, milk, vanilla and salt in a bowl.

Divide batter into muffin cups. Top with caramelized apples and crumb topping.

Bake for 5 min at 200C (425F) then reduce the temp to 190C (375F) without opening the oven door. Bake for another 15 min or until the toothpick inserted comes out clean.

Top with icing and serve once cooled.