Place the butter and sugar in a bowl and beat with an electric mixer until pale and fluffy. Add the vanilla, then the eggs one at a time, mixing with each addition.

In a separate bowl, mix together the flour, baking soda and salt. Add this to the butter mixture in 2 additions, alternating with the sour cream. Add the confetti sprinkles and mix to combine.

Pour the batter into a greased and floured 9x13 inch pan and smooth the surface. Bake at 350F for 40-50 minutes, until a skewer inserted into the center comes out clean. Cool completely.

If you are making double digits, repeat the process to make the second cake. If you want to make the batter for both cakes in one batch, you’ll need a BIG bowl!

Beat the butter with an electric mixer until pale and fluffy. Add the vanilla extract and mix to combine.

Add the confectioner’s sugar one cup at a time, then mix for 3-4 minutes, until light and fluffy.

Add a couple drops of pink food coloring to dye it a pale pink color.

Use an edible ink pen to draw the number onto the surface of the cake, in a block letter style. Make sure the number is as thick as possible, approximately 4-5 inches wide at each point.

Use a serrated knife to carve the cake along the lines. Then round the edges of the number, to make it look like a rounded balloon. Place the cake on a cake board at this point, as the odd shape of the cake will make moving it difficult, once it is frosted.

Cover the entire cake in a thin layer of buttercream. Place the cake in the fridge for 20 minutes, to chill. Then coat the cake in a generous layer of buttercream. Smooth the buttercream as much as possible.

Place the remaining buttercream into a piping bag fitted with a large, angled piping tip. Place the widest side of the piping tip against the cake and pipe a ruffle around the entire number.

Spray the entire cake with the metallic food spray. To protect the rest of your kitchen, use your hand or a sheet of paper to catch the overspray on the opposite side of the cake. Enjoy!