Instructions

1. Line a 12-hole muffin tray with cupcake liners. Preheat oven to 180 C (350 F) standard / 160 C (320 F) fan-forced.
2. In a large mixing bowl, add butter and sugars and beat with an electric mixer on medium speed until pale and creamy. Add vanilla and egg and beat briefly just until combined.
3. In a separate bowl, add flour, baking powder, cinnamon and salt and whisk briefly.
4. Add flour mixture to the butter mixture, along with buttermilk and the mashed banana. Gently mix until just combined. The batter will be thick and creamy.
5. Spoon batter into prepared cupcake liners and bake for approximately 18-20 minutes or until the cakes spring back lightly to the touch. Remove cupcake from muffin tray and place on a wire rack to cool completely. 
6. To make the cream cheese frosting, add butter and cream cheese (ensuring both are at room temperature) to a large mixing bowl. Beat with an electric mixer on medium speed for 2-3 minutes until smooth and creamy. Add vanilla.
7. Add sugar, 1 cup at a time, and continue to beat on a medium speed until smooth. Transfer frosting to a large piping bag fitted with a large round tip. Pipe frosting onto each cupcake. Scatter over crushed walnuts.