Preheat oven to 180C and line a 12 cup muffin tray.
Peel and place bananas and apple puree in a blender and process until smooth.
In a bowl, sift all dry ingredients and add banana apple mixture.
Mix until just combined, don't over stir, and pour into muffin tray.
Bake for 20 - 25 minutes or until skewer comes out clean.
Place on cooling rack until completely cool.
Remove hazelnut cream from refrigerator and stir until creamy and smooth. Spoon into a piping bag that has a filling tip attached. I use the Wilton 230.
Insert filling nozzle into the middle of the muffin at a 90 degree angle and fill until you see the top of the muffin start to bulge.
Change piping nozzle and pipe remaining cream on top and sprinkle with chopped hazelnuts. Alternatively you can top with frosting of choice. Something chocolate-y would be awesome!