Preheat the oven to 350 degrees F (180 degrees C).
In a blender, puree the Banana (3) and Mango Purée (1/2 cup) together.
Melt the Butter (8 tablespoon) and set aside. Beat the Egg (2) and set aside.
In a bowl, mix together the All-Purpose Flour (1 1/2 cup), Granulated Sugar (3/4 cup), Baking Powder (1 teaspoon), Baking Soda (1 teaspoon) and Salt (1/4 teaspoon). Form a hole in the middle of the bowl.
Add the fruit puree, butter, eggs, and Vanilla Extract (1/2 teaspoon) into the hole and and gently fold the wet ingredients in using a spatula.
If using, add the Assorted Nuts (to taste) and fold them in. Line a muffin mold with paper liners and fill them with the batter.
If using, decorate with Sprinkles (to taste) and bake for 15-20 minutes. To check if they are done, insert a toothpick; if it comes out clean the muffins are done. Let muffins cool before eating.