Ensure that you have all your ingredients measured and ready to use.
Preheat your oven to 180 Degrees C (355F).
Cut some non-stick baking paper to line the base of a 20 cm (8 inch) springform tin and grease the sides.
Combine the flour and baking soda, sift them together and set aside.
In the bowl of a stand mixer fitted with the paddle attachment, or using hand-held electric beaters, combine the room temperature butter and caster sugar.
On medium speed, beat for about 3 minutes until the mixture is a pale, creamy colour. Scrape down the sides of the bowl as necessary to ensure the mixture is well amalgamated.
Add the eggs, one at a time, beating well after each addition, and scrape down the sides of the bowl occasionally. Add the mashed bananas and vanilla extract and combine. The mixture may appear to curdle at this point, but it will come together.
With the mixer on the lowest speed, add half the sifted flour mixture alternately with half the milk until only just combined. Do not overbeat. Remove the bowl, use a silicone spatula to combine any remaining flour.
Turn the mixture into the prepared baking tin, and place into the preheated oven. Cook for 35-40 minutes or until a fine skewer inserted into the centre of the cake comes out clean.
Place the tin onto a metal cooling rack. After about 10 minutes, remove the side of the tin. Allow the cake to cool completely. Transfer to a serving plate and then top with the frosting.