Preheat the oven at 180 °C.
Butter the pan of your choice (Bundt, bread pan, rectangular pan), and dust with flour.
Mix the flour with salt, baking soda and baking powder.
On a plate, smash the bananas with a fork,
Chop the chocolate.
Separately, using a whisk or a hand mixer, beat the butter with the sugar and vanilla.
After it gets fluffier and creamier, add one egg at a time.
Add the banana.
Using a spatula, and folding motion, add alternately the flour mixture and the sour cream/yogurt.
Mix fast and only until the flour is almost incorporated. Do not overmix, the texture of the cake will be too dense.
Add the chocolate and fold a few times.
Pour the batter into the baking pan of your choice and bake around an hour.
The cake is done when a toothpick or knife inserted in the middle of the cake comes out clean.
Cool for 5 minutes in the pan, then flip it on a cooling rack and cool completely.
It tastes better the second day if you feel you can wait for it.