Pre-heat the oven to 180°C; prepare a 6 inch baking pan with parchment paper, lining and greasing the baking tin well.
Beat the butter and sugar together in a mixing bowl until light and fluffy.
Add the egg and beat again until the mixture is creamy. Now beat in the scraped vanilla bean.
Sift the all-purpose flour into a separate bowl. Add the baking powder and salt and give it a good whisk to make sure that the dry ingredients are evenly combined.
Add half of the dry ingredients and all of the milk to the wet mixture. Beat on a low speed (with your hand mixer) until evenly combined.
Then add the remaining flour along with the yogurt; beat again on a low speed until just combined and the batter is thick and creamy.
Add the sprinkles, gently folding them in using a rubber spatula. Don’t over-mix at this stage, as if you do the cake will be more dense and less fluffy.
Pour the cake batter into the prepared baking tin and smoothen the top. Bake for around 25 – 30 minutes or so until the cake is golden and a toothpick/ knife plunged in the centre will emerge clean. While the cake is cooling down, make the frosting: