Mix the flours, baking powder and baking soda together and set aside.
Peel the apple and remove the core. You need exactly 100g. Grate the apple finely and also catch the juice. Set aside.
Peel the mango and cut off 100g. Slice it into very small cubes.
Mash the banana in a big mixing bowl. Add the egg, the grated apple and a pinch of salt. Use a handheld mixer and whisk everything for about two minutes.
Pour in the milk and the oil. Keep mixing.
Add the flour mix in one go and keep mixing.
Pre-heat the oven to 180 degrees Celcius.
Mix the mango cubes into the dough with a spatula. Fill 10 muffin forms on a muffin tray evenly with the dough.
Bake the muffins for 30-35 minutes. Leave them to cool for about ten minutes before you take them out of the moulds. Then leave them to cool completely before you transfer them into an air-tight box for storage. Serve your muffins the next day.