Preheat the oven to 375 (F); for sea-level, preheat the oven to 325 (F).
Put 1 cup flour, a scant 3/4 cup sugar, 1 tablespoon baking powder, 1 teaspoon cinnamon, 1 teaspoon ginger, a 5 tablespoons butter, and a pinch of salt in a freestanding electric mixer with a paddle attachment (or use a handheld whisk) and beat on slow speed until you get a sandy consistency and everything is combined.
Slowly pour 1/2 cup milk into the flour mixture, beating well until all the ingredients are well mixed.
Add 2 eggs and beat well, scraping any unmixed ingredients from the side of the bowl with a rubber spatula. Stir in 1 mashed banana by hand with a rubber spatula until evenly dispersed.
Spoon the batter into paper cases in your muffin tin until two-thirds full and bake in the preheated oven for about 20 - 24 minutes, or until light golden and the cake bounces back when touched.
Let the cupcakes cool slightly in the pan before turning out into a wire rack to cool completely. When the cupcakes are cold, spoon the Chocolate Frosting (recipe follows) on top and finish with chocolate shavings.