Preheat the oven to 325°F Insert liners into medium cupcake pans.
Prepare cupcakes: in a bowl, sift flour, baking powder, salt and nutmeg.
Place butter and sugar in mixing bowl, beating with the mixer's flat beater on medium speed until mixture is light and airy.
Reduce speed to low, add eggs one at a time, mixing well.
Add half the flour mixture (prepared in step 2), banana purée and then remaining flour mixture.
Finally, add chocolate shavings and stir.
Fill the cupcake liners two-thirds full.
Bake for 20-25 minutes, or until cupcakes are springy to the touch and a toothpick inserted in cupcake's center comes out clean.
Remove from oven and cool on wire for 10 minutes.
Prepare frosting: in an electric mixer, beat cream cheese for about 2 minutes, untill cheese is soft and smooth. Add powdered sugar and banana liqueur. Continue beating mixture until frosting is smooth.
With a spatula, spread frosting on each cooled cupcake, garnish with sliced bananas and chocolate shavings.