VANILLA BUTTERMILK CAKE

1. Position a rack in the center of your oven and preheat the oven to 350°f / 180°c. Butter or coat an 8" square baking pan with nonstick spray. Line the pan with a strip of parchment paper that hangs over two of the edges. 
2. In a large bowl, whisk the sugar and egg until pale and foamy, about 1 minute. Add the buttermilk, butter, oil, vanilla, and salt. Whisk until smooth and emulsified.
3. Add the flour, malted milk powder, baking powder, and baking soda and whisk until well combined and smooth. 
4. Pour the batter into the prepared pan, tap the pan gently on the counter to release any air bubbles, and smooth the top of the batter with an offset spatula.
5. Bake the cake until puffed and golden, and a tester inserted into the centre comes out clean, 30 to 40 minutes. Set the pan on a rack to cool for about 15 minutes. Then use the parchment paper to lift the cake out of the pan and set it on a rack to cool completely.

CHOCOLATE FROSTING

1. Add the butter to a large bowl and mix with an electric mixer on medium-high until smooth and creamy.
2. Turn the mixer onto low, add the cocoa powder, and mix until smooth, scraping the bottom and sides of the bowl as necessary, then slowly add the powdered sugar.Mix until the sugar is moistened, then add the vanilla, a pinch of salt, and 1-2 Tbsp milk.
3. Turn the mixer to medium high and whip until light and fluffy, adding more milk as necessary to make a smooth and fluffy frosting.
4. Top the cooled cake with swoops of frosting and scatter with sprinkles. 
5. Store covered, at room temperature, or in the fridge for up to 3 days.