1. Bake x2 of the Vanilla Spongecake using 25cm tins at least a day before you plan to decorate it.
Note: If you know your baking isn’t cooked through but it’s looking crusty on top, carefully place a sheet of tinfoil on top of the cake. This will stop it from getting any darker on top but will allow the cake to continue cooking until it’s fully done.
2. Make the buttercream
Beat butter in an electric mixer, using a paddle attachment, until the butter lightens in colour. Slowly add icing sugar in small batches (so it doesn’t fly out of the mixing bowl), beating in between until combined. Add milk 1 tablespoon at a time.
Note: Start with room-temperature butter (not melted) and to beat with an electric mixer until the butter turns from a yellow to a white tone before adding icing sugar. Buttercream can be stored in an airtight container for up to 2 weeks in the fridge, but bring it back to room temperature and beat again before using so it is as light, fluffy and soft as possible
3. To Make The Blocks:
Cut the pink wafers into 7 cm squares using the tip of a serrated knife.
Melt the white chocolate in a double boiler or microwave. Smoothly spread white chocolate on one side of each wafer square and set aside on baking paper to dry. Once the squares are dry, you can start forming them into 3 cubes using leftover chocolate as the ‘glue’ to join them together. Join the first 3 sides, holding them momentarily until the chocolate hardens, then add the remaining 3 sides one at a time, again holding each one in place until the chocolate has hardened. Set cubes aside to fully dry. (If it is a hot day, or to speed up the process, you can put them in the fridge.)
Thinly roll out the red fondant and cut it into 12 lengths measuring 2 cm x 7 cm. Cut each end of these lengths into a small point. Place the lengths along the edges of one of the cubes, making sure the strips sit evenly on each side of the joins and that the 3 fondant points meet neatly in each corner. (Use a small amount of buttercream to stick the fondant to the white chocolate if necessary.)
Roll out the leftover red fondant and punch out 6 letter A’s with the cookie cutter. Stick them to the middle of each cube side with a little buttercream.
Repeat this process for the remaining cubes, using blue fondant for one and yellow fondant for the other, punching out a different letter for each block.
Level the cakes using a cake leveler if possible. Turn cakes over.
Take the first cake for the stack and evenly spread buttercream over the top surface, then place the next layer on top.
Crumb coat the cake by applying a thin layer of buttercream with a palette knife or offset spatula to achieve a very thin, smooth finish (you should be able to see the cake through the icing). Never wipe excess crumb-coat icing back into the main bowl of icing as it will be full of crumbs and spoil the rest of the icing.
Refrigerate cake until dry to the touch.
Cover the entire cake with buttercream to a smooth finish.
Push a row of red M&M’s into the buttercream around the bottom edge of the cake. Directly above the red row, add a row of yellow M&M’s, slotting them into the gullies formed by the M&M’s in the row below. Repeat with a layer of blue M&M’s. Continue the stripy pattern all the way up the side of the cake.
Arrange the blocks on the centre of the cake.
Note: The blocks can be made up to a week in advance and stored in an airtight container. If making more than 3 blocks, remember to allow 6 wafers per block.