Preheat oven to 350°F (175°C). Line 8x8-inch pan with parchment paper.
Mash bananas in large bowl until smooth.
Mix melted butter and sugar until combined.
Add mashed bananas, then beat in eggs one at a time. Stir in vanilla.
Whisk together cocoa powder, flour, and salt in separate bowl.
Fold dry ingredients into wet mixture until just combined.
Stir in chocolate chips.
Pour into prepared pan, spread evenly.
Bake 25-30 minutes until toothpick has moist crumbs.
Cool completely before cutting.
Top with whipped cream and banana slices before serving.