Preheat oven to 180C fan.
Choose and prepare cake tins.
In a stand mixer fitted with the paddle attachment, cream together the butter and two sugars until fluffy.
Add eggs, one at time whilst keeping the mixer on medium speed.
Add sour cream and vanilla extract.
In a medium bowl, combine flour, bicarb, salt.
Turn mixer to low and slowly spoon in the flour mixture until it is complete incorporated into the batter.
Turn off the mixer and gently fold in the mashed bananas.
Gently pour into prepared cake tins.
Bake. Bake time will vary based on cake tins sizes. When a toothpick or skewer comes out clean, they are done.