Preheat oven to 180 degrees. Grease a 6-muffin pan or line it and set aside.
Combine the flour, sugar, salt and baking powder in a bowl and whisk well to combine.
In another bowl, whisk the coconut milk and flax egg well. Add to the dry ingredients and fold in.
Grind the mango and banana into a paste, you can leave a bit of bites. Add this to the mixture and fold in gently till fully moist.
Divide equally into the prepared muffin pan.
Mix all the ingredients for the struesel till well combined and sprinkle over the muffins.
Bake in the oven for 20 to 25 minutes till a skewer comes out clean.
Cool in pan for 10 minutes before removing from the pan and cooling on the rack completely.
Serve with a cup of coffee!