Step 1

Preheat the oven to 350°F (175°C). Butter three 9-inch (23-cm) round cake pans. Dust with a few tablespoons of flour, then tap out the excess.

Step 2

Chop the butter into small, pea-size pieces and return them to the refrigerator. Bring the milk to room temperature by zapping it in the microwave for 30 seconds, then add the vanilla and set it aside.

Step 3

In the bowl of a stand mixer fitted with the paddle attachment, combine the flour, 2 1/2 cups (500 g) of the sugar, the baking powder, and salt. Mix on low for 30 seconds. Add the cold butter to the flour mixture and bring the speed up to medium. Mix until the butter breaks down and the flour mixture is the texture of wet sand. Bring the speed back down to low and add the milk mixture. Transfer the mixture into a large bowl and set aside.

Step 4

Fully clean and dry out the bowl of the mixer, swap out the paddle for the whisk attachment, and add the egg whites and remaining 1 1/2 cups (300 g) sugar to the bowl. Whisk on high until the mixture forms soft peaks. Gently fold the meringue into the flour and milk mixture until fully incorporated.

Step 5

Divide the batter equally between the prepared pans and bake them for 30 to 40 minutes, rotating halfway through, until they are golden brown and a cake tester comes out clean.

Step 6

Transfer the pans to a wire rack for 10 minutes before turning the cakes out of the pans to cool completely. Using a serrated knife, trim the tops off the cakes to make them level and frost and stack the three layers. Decorate the side with rainbow sprinkles and the top with frosting rosettes. Serve a slice with a glass of bubbly.

Step 7

Store at room temperature in a cake dome or large plastic Tupperware for up to 3 days.

Step 8

In the bowl of a stand mixer fitted with the paddle attachment, cream the butter, making sure to stop the mixer every so often to scrape down the sides and bottom of the bowl. It’s important to have all the butter nice and soft so you don’t get any clumps of cold butter when trying to pipe the frosting. Next, add the cream cheese a quarter at a time on medium speed. When it is incorporated, add the vanilla. Turn the mixer to the lowest speed and slowly add the sugar. Finally, crank the mixer up to high speed and beat it for 30 seconds, until fully blended and fluffy.

Step 9

Makes enough for one 8-inch (20-cm) cake, 4 dozen mini-cupcakes, or 1 dozen regular-size cupcakes