Instructions

1. Preheat oven to 350 F (175 C). Grease and flour sides of three 8-in (20 cm) cake pans. Line bottom of pans with parchment. Set aside.
2. Place a sieve over a large bowl and sift in 350 g (about 2½ cups/625 ml) flour, ½ tsp (2.5 ml) baking powder and ¼ tsp (1 ml) salt. Set aside.
3. In a separate large bowl, beat 1 cup (250 ml) butter until softened. Add 350 g (about 1¾ cups/430 ml) sugar, ½ cup (125 ml) oil and 1½ tbsp (22.5 ml) vanilla extract and beat until pale and fluffy.
4. Add 1 egg and beat until fully incorporated. Similarly, continue with 3 more eggs (one at a time), for a total of 4 eggs.
5. Fold in half the flour mixture until no streaks remain. Mix in 3 tbsp (45 ml) milk, then fold in remaining flour mixture until fully incorporated. Divide batter equally between 3 medium bowls.
6. Add purple food colouring to 1 bowl and mix until no streaks remain. Pour into a prepared cake pan. Repeat with blue in second bowl and cake pan, and green in third.
7. Bake for 30 to 35 minutes, until a toothpick inserted in centre of each cake comes out clean. Remove from oven and cool in pans for 5 minutes, then remove cakes from pans and cool on a wire rack.
8. Repeat above process to make 3 more bowls of batter. Add yellow food colouring to 1 bowl and mix until no streaks remain. Pour into a prepared cake pan. Repeat with orange in second bowl and cake pan, and red in third. Bake and cool as directed above.
9. Cut off any domed tops of cakes for even, flat cake discs.
10. To assemble, smear about 1 tbsp (15 ml) American Buttercream in centre of a serving platter and reserve 1 cup (250 ml) for later use. Centre purple cake layer on platter. Transfer remaining buttercream to a large piping bag with no nozzle. Pipe circles of icing around top of cake, starting from outer edge and working to the centre. Use a metal spatula to evenly spread icing on surface of cake about ¼-in (0.6 cm) thick. Repeat layering cake and frosting in this manner with blue, green, yellow and orange cakes. Finally, place red cake on top, but do not frost it.
11. Cut a 7½-in (19 cm) circle out of parchment. Lay the parchment on top of cake and use it as a guide to trim off browned edges with a sharp knife. Using a metal spatula, cover sides and top of cake with a thin layer of remaining American Buttercream and chill cake for about 2 hours.
12. Remove cake from refrigerator. Using a metal spatula, cover sides and top with Stabilized Chantilly Cream.
13. Place cake on a large baking sheet. Swiftly throw small handfuls of flaked coconut onto sides and top of cake. Reuse any excess that falls onto baking sheet to completely and evenly cover cake. Use reserved buttercream to pipe rosettes or other shapes, and decorate as desired with bonbons.
14. *For best results, flour and sugar should be weighed for this recipe. The approximate volumes shown are based on 1 cup (250 ml) flour = 140 g and 1 cup (250 ml) sugar = 200 g.
15. American Buttercream: In a very large bowl, beat butter, salt and vanilla extract until smooth and well incorporated. Add 1 cup (250 ml) icing sugar at a time and mix well after each addition. If needed, add 1 tbsp (15 ml) milk at a time and continue beating to desired consistency. Can be made ahead and stored in an airtight container in refrigerator for up to 3 days. Bring to room temperature before using as needed. Makes about 16 cups (4 L)
16. Stabilized Chantilly Cream: In a large bowl, whisk all ingredients until soft peaks form. Use immediately or store in an airtight container in refrigerator for up to 1 day. Makes about 4 cups (1 L)