- 7 eggs, at room temperature
- 7 egg yolks, at room temperature
- 400 gm caster sugar
- 250 gm plain flour
- 140 gm cornflour
- ¾ tsp baking powder
- 100 gm hazelnut meal
- 250 gm butter, melted and cooled, plus extra for greasing
- 130 ml vegetable oil
- 300 gm mascarpone
- 20 gm brown sugar
- 2 tbsp espresso-strength coffee mixed with 1 tbsp coffee-flavoured liqueur
- Chocolate curls and gold cachous, to serve
- 100 gm eggwhite
- 100 gm caster sugar
- 100 gm pure icing sugar, sieved
- 1½ tbsp Dutch-process cocoa
- 2 tsp cornflour
- 2 tsp very strong espresso coffee
- 300 ml pouring cream
- 300 gm dark chocolate (50%-60% cocoa solids), coarsely chopped
- 40 gm unsalted butter
- 20 gm liquid glucose
- 300 ml pouring cream
- 80 ml coffee-flavoured liqueur
- 300 gm dark chocolate (50%-60% cocoa solids), finely chopped
- 100 gm milk chocolate, finely chopped
- 4 egg yolks
- 1For mocha meringue, preheat oven to 100C, and line 2 oven trays with baking paper. Whisk eggwhite, caster sugar and ½ tsp sea salt in an electric mixer until glossy soft peaks form (3-4 minutes). Sieve in icing sugar, cocoa and cornflour, fold to combine, then fold in coffee. Spread mixture 1cm thick on prepared trays, then bake until crisp but not coloured (1¼-1½ hours). Cool completely on trays, then store between layers of baking paper in an airtight container until required. Meringue can be made 2 days ahead; crumble it just before serving.
- 2For truffle filling, bring cream and half the coffee liqueur to the boil. Remove from heat, add chocolates and stand for 5 minutes, then whisk until smooth. Whisk yolks and remaining liqueur in a bowl over a saucepan of simmering water until pale and fluffy (2-3 minutes), then whisk in chocolate mixture, transfer to an electric mixer and whisk until cooled to room temperature (5-6 minutes). Transfer to a container, cover and refrigerate overnight to set. Filling can be made a week ahead.
- 3Preheat oven to 180C, and butter a 10cm diameter cake tin, a 16cm-diameter cake tin and a 21cm-diameter cake tin, line the bases with baking paper and dust with flour. Whisk eggs, egg yolks, sugar and a good pinch of salt in an electric mixer until thick, pale and tripled in volume (5-6 minutes). Meanwhile, triple-sieve flour, cornflour and baking powder into a bowl, then stir in hazelnut meal. Transfer egg mixture to a large bowl, fold in hazelnut mixture in 3 batches, then fold in butter and oil. Pour into prepared cake tins, filling to 1.5cm below rims and bake, swapping tins occasionally, until centres spring back when lightly pressed (40-45 minutes for small cake; 50-55 minutes for medium cake; 50 minutes to 1 hour for large cake). Cool in tins for 5 minutes, then turn out onto wire racks to cool completely (1 hour).
- 4For chocolate ganache, bring cream just to the boil in a saucepan, remove from heat, add chocolate, butter and glucose, stand for 5 minutes, then whisk until smooth and just combined (don’t overwhisk or mixture can split). Transfer to a container and refrigerate, stirring occasionally, until spreadable (5-6 hours).
- 5Whisk mascarpone and brown sugar in a bowl to firm peaks (1-2 minutes; don’t overwhisk or it will curdle) and refrigerate until required.
- 6Halve each cake horizontally and brush cut sides with coffee mixture. Spread or pipe truffle filling to 1cm thick on each base, top with crushed mocha meringue, spread or pipe mascarpone over to 1cm thick and sandwich with top halves. Spread tops and sides of cakes with ganache with an offset palette knife dipped in hot water. Stack cakes, ascending to smallest, decorate with chocolate curls and gold cachous, and serve.
For chocolate collars, cut strips of acetate long enough to wrap around each cake and spread thinly with melted, preferably tempered dark chocolate. Wrap around cakes once they’re assembled, chocolate side in, refrigerate until set, then carefully peel back the acetate, decorate and serve.