With the rack in the middle position, preheat the oven to 180 °C (350 °F). Butter a 20-cm (8-inch) in diameter springform pan. Line the bottom with parchment paper.
In a bowl, combine the flour, baking powder, baking soda and salt. Set aside.
In a plate, using a fork, mash the bananas until smooth. Set aside.
In another bowl, cream the butter with the oil, sugar, and vanilla with an electric mixer. Add the eggs, one at a time and beat until incorporated. At low speed, add the dry ingredients alternately with the milk and bananas. Spread in the pan. Bake for about 1 hour and 15 minutes or until a toothpick inserted in the centre of the cake comes out clean. Let cool. Unmould and cool completely on a rack.
Mars Bar Ganache
In a saucepan, completely melt the Mars bars with the cream, stirring frequently. Let cool and spread on the cake.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.