Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round cake pan, or use parchment paper at the bottom.

In a large mixing bowl, cream together the softened butter and sugar until light and fluffy.

Beat in the eggs one at a time, then add mashed bananas and vanilla extract. Mix until combined.

In another bowl, whisk together flour, baking soda, baking powder, and salt. Gradually add this mixture into your banana mixture, stirring gently until just combined.

Fold in the chopped walnuts.

Pour the batter into your prepared cake pan and bake for about 25-30 minutes, or until a toothpick inserted in the center comes out clean.

While the cake is cooling, whip heavy cream until soft peaks form. Add the powdered sugar and vanilla extract, continuing to whip until stiff peaks form.

Once the cake is cool, slice it in half horizontally. Spread a layer of cream filling between the two layers and top with the remaining cream.

Sprinkle with extra chopped walnuts for presentation.

For best results, let the assembled cake chill in the refrigerator for about an hour before serving.