In a bowl sift together all purpose flour, salt and baking powder. Set aside.
In the steel bowl of your stand mixer fitted with paddle attachment or using a hand mixer beat together oil and egg for 3-4 minutes till it's creamy and doubles in volume.
Add sugar to the egg-oil mixture and beat for 2-3 minutes till well incorporated.
Add in the mashed bananas, vanilla and mix till combined
Start adding the flour and milk in parts, starting and ending with the flour.
Mix till well combined but do not overmix. Your batter is now ready.
Fill the cupcake liners with the batter till half full.
Bake at 350 F degrees for 18-20 minutes or till a toothpick inserted in the center comes out clean. Mine were done in 18 minutes,
Filling
Attach wilton tip 230 to a pastry bag and fill it with nutella.
Take a cupcake and insert the tip in the center going more than halfway down and then pushing in the nutella as you take the tip out.
Repeat the same till all cupcakes are filled with nutella.
Frosting
Before you make the frosting, chill the bowl of your mixer and your whisk attachment in the refrigerator for 20-30 minutes.
Pour heavy cream in the steel bowl of your stand mixer fitted with whisk attachment or use your hand mixer.
Beat the cream at high speed till it thickens [2-3 minutes] and then add vanilla, powdered sugar and nutella.
Beat the cream on high till it forms stiff peaks. The total process takes around 6-7 minutes to form still peaks.
Pipe the frosting on cooled cupcakes and decorate with rainbow sprinkles!