Vegan Chocolate Charlotte

Line a 15 cm round springform tin or charlotte mould with cling film, leaving enough overhang to fold over the top. Open the chilled tin of coconut cream and scoop the solidified cream into a bowl, discarding or reserving the liquid. Separate the aquafaba into a large, grease-free mixing bowl. Finely chop the chocolate. Combine the cooled espresso and rum (if using) in a shallow dish wide enough to dip the biscuits.

Melt the chopped chocolate and coconut oil together in a heatproof bowl set over a saucepan of barely simmering water, stirring until completely smooth. Remove from the heat and stir in the vanilla extract and salt. Set aside to cool to room temperature, about 15-20 minutes — the mixture must not be warm when folded or it will deflate the mousse.

Whip the chilled coconut cream with a hand mixer on medium-high speed until soft, billowy peaks form, about 3-4 minutes. Transfer to the refrigerator.

Add the cream of tartar to the aquafaba and whip with a clean hand mixer on medium speed until foamy, about 2 minutes. Gradually rain in the caster sugar, one tablespoon at a time, then increase to high speed and whip until the meringue holds stiff, glossy peaks that do not droop, about 8-10 minutes.

Fold the cooled chocolate mixture gently into the whipped coconut cream with a rubber spatula using wide, sweeping strokes until just combined.

Add one-third of the aquafaba meringue to the chocolate-coconut mixture and stir to loosen. Fold in the remaining meringue in two additions, cutting through the centre and turning the bowl, until no white streaks remain and the mousse is uniform and airy.

Working quickly, dip each boudoir biscuit into the espresso mixture for 2-3 seconds per side — they should be moistened but not sodden. Stand the dipped biscuits upright around the inside wall of the prepared tin, sugar side facing outward, trimming to fit as needed.

Arrange a single layer of dipped biscuits flat across the base of the tin, cutting to fill any gaps. Pour in half the chocolate mousse and spread level. Add a second layer of dipped biscuits across the middle, then pour in the remaining mousse and smooth the top with a palette knife.

Fold the cling film overhang over the surface and refrigerate for a minimum of 6 hours, or overnight, until fully set and sliceable.

To serve, unfold the cling film, invert the charlotte onto a serving plate, and carefully remove the tin and cling film. Dust the top with cocoa powder and scatter the toasted hazelnuts over. Slice with a warm, dry knife.