Banana cake:
Preheat the oven to 350°F (180°C).
Generously butter a 9″ (23cm) round mold with removable sides and line the bottom with parchment paper. Set aside.

In a bowl, combine the flour, baking powder, baking soda, and salt. Set aside.
In the mixer bowl, with the whisk, cream the butter, oil, and sugar.
Add the eggs one by one, whisking well between each addition.
Incorporate the banana puree and vanilla extract and mix well.
Add the reserved dry ingredients, alternating with the milk. Mix well.

Pour the preparation into the mold and bake for 1 hour 10 minutes, or until a toothpick inserted in the center comes out clean.
Let rest for 10 minutes in the mold before unmolding the cake onto a grid and letting it cool completely.

Mars glaze:
In a stainless steel bowl, put the cream and the pieces of Mars bars.
Melt in a double boiler, whisking, until the texture is smooth.
Let temper before spreading the preparation over the banana cake.