2.To make macarons, beat egg whites and caster sugar in medium bowl with electric mixer until soft peaks form and sugar is dissolved.
3.Meanwhile, blend or process icing sugar, ground almonds and coconut until fine and powdery. Sift through fine strainer; discard solids in strainer.
4.Transfer egg white mixture into large bowl. Fold in almond mixture in two batches.
5.Fit large piping bag with tube. Half-fill bag with macaroon mixture. Pipe 50 x 2cm (¾-inch) rounds about 2cm (¾-inch) apart onto trays. Pipe 50 x 3.5cm (1½- inch) rounds about 2cm (¾-inch) apart onto trays. Pipe 50 x 4.5cm (1¾-inch) rounds about 2cm (¾-inch) apart onto trays. Refill bag with macaron mixture as needed. Tap trays on bench so macarons spread slightly. Stand macarons for about 1 hour or until they feel dry to touch and have developed a ‘skin’.
6.Preheat oven to 120°C/250°F.
7.Bake small macarons, in batches, about 15 minutes. Cool on trays. Bake remaining macarons, in batches, about 20 minutes. Cool on trays.
8.Line inside the croquembouche mould with plastic wrap.
9.Cut a 5cm (2-inch) and a 17cm (6¾-inch) round from the coconut cake (push a cake pan or plate firmly into the cake to leave a mark to use as a guide). Place the small round of cake inside croquembouche mould. Use the ice-cream scoop to scoop rounds of cake; chop remaining cake coarsely.
10.Using half the ganache, pack the mould with a random mix of cake and dollops of ganache. Top with the large round of cake; press down firmly. Refrigerate tower for 3 hours or overnight until firm.
11.Secure cake tower to board with a little ganache; remove the croquembouche mould. Remove plastic wrap; spread tower all over with remaining ganache.
12.Using skewer, gently push small pieces of gold leaf onto macarons. Gently press large macarons around bottom of the cake, followed by the medium macarons, then the small macarons at the top.
Equipment: oven trays, large piping bag 1.5cm (¾-inch), plain piping tube 25cm (10-inch), deep croquembouche mould (diameter 18cm/7¼-inch), medium-sized ice-cream scoop 25cm (10-inch), round wooden cake board, wooden skewer If you prefer, make the macaroons in 2 or 3 batches. Base the proportions on 2 or 3 egg whites (either a third or half of the recipe ingredients) and use a small bowl for beating the egg whites and sugar mixture. Ovens are often inaccurate at low temperatures, so reduce the oven temperature if the macaroons are browning. The tower of cake can be made at least a week ahead, and frozen or refrigerated. The ganache coating and macaroons should be positioned on the day of serving. Gold leaf is delicate and fiddly to handle, but worth the effort. The coconut cake can be kept at room temperature in an airtight container for a week or frozen for up to 2 months. Choose the best macarons for the tower. Leftovers will keep in an airtight container at room temperature for at least a week, or can be frozen for about 6 weeks. Make sure you have room in the fridge for the cake to set. You need to make about 150 macarons (we made extra in case of breakages), so it is probably easier to make them in 2-3 batches. Make sure you have plenty of oven trays. Draw circles the size of the macarons onto the back of the baking paper to use as a guide when piping the rounds.