Step 1

Grease and line two 8 inch round cake pans. Preheat oven to 180 C (350 F) standard / 160 C (320 F) fan-forced.

Step 2

In a large mixing bowl, add butter, sugar and vanilla and beat with an electric mixer on medium speed until smooth and creamy. Add eggs, one at a time, and beat after each addition.

Step 3

In a separate bowl, add flour, baking powder and salt, and whisk briefly. Add half of the flour mix and all the milk and beat on a low speed until combined.

Step 4

Add remaining flour mix and sour cream and continue to mix on a low speed until just combined and a thick, creamy cake batter forms. Gently fold in sprinkles by hand, being careful not to overmix.

Step 5

Divide the batter evenly between the two cake pans and bake in the oven for approximately 25-30 minutes or until golden and a knife inserted in the middle comes out clean.

Step 6

Carefully remove the cakes from pans and set on a wire rack to cool completely.

Step 7

To make your frosting, roughly chop butter into cubes and place in a large mixing bowl. Beat with an electric mixer on medium speed for 1-2 minutes or until your butter is smooth and creamy. There should be no lumps. Scrape down the sides of the bowl.

Step 8

Add vanilla and beat briefly to combine. Then add 125 grams (1 cup) sugar. Beat on a low speed to combine, then turn up the speed to medium and mix for 30 seconds or so. Mixture should be thick and appear a little dry – this is fine.

Step 9

Next, add another 125 grams (1 cup) sugar, along with 1 tablespoon of milk. Beat on medium speed until combined. Scrape down the sides of the bowl.

Step 10

Add another 125 grams (1 cup) sugar, along with 1 tablespoon of milk. Beat on medium speed until mixture is thick and creamy.

Step 11

Finally, add remaining 125 grams (1 cup) sugar and beat on medium speed until mixture is smooth. Buttercream should be lovely and thick at this stage with no lumps.

Step 12

If the buttercream is too thick, add an extra tablespoon or two of milk. To finish, give your buttercream a good stir by hand using a spatula.

Step 13

Trim the tops of cake if needed. Place one cake on a cake plate, and cover the top with buttercream. Place the second cake on top. Cover the entire cake, top and sides, with remaining buttercream.

Step 14

Pick up the cake and hold over a large mixing bowl. Carefully press sprinkles into the side of the cake, letting the extra sprinkles fall into the bowl. Continue until top and sides of cake are completely covered.

Step 15

Place cake in the fridge for 10-15 minutes to for the frosting and sprinkles to set slightly. Cut into slices and serve.