- 150 g (⅔ cup) caster sugar
- 1 lemon, juiced or 1/4 cup water
- ½ vanilla bean, split and seeds scraped
- 400 g fresh or frozen blueberries
- 10 g gelatine powder
- 2 egg whites
- A pinch of cream of tartar
- 100 ml pouring (whipping) cream
- Sponge cake, sliced
- Fresh blueberries for garnish
- Combine water (or lemon juice), caster sugar, vanilla bean, and blueberries in a small saucepan and bring to a simmer over low heat. Cook for 5 minutes, and then remove from the heat. Transfer half the cooked blueberries to a bowl to cool. Place the remaining berries in a fine sieve placed over a bowl and press down to extract as much purée as possible. Discard the solids.
- Whisk the gelatine into the warm purée until it has all melted, then refrigerate until cool but not set.
- Using an electric beater, whisk the egg whites and cream of tartar until stiff peaks form. Whisk in the remaining sugar until glossy and the sugar has dissolved.
- Next, whisk the cream until soft peaks form, then fold into the cold blueberry purée. Gently fold in the beaten egg whites. Spoon the mousse into layers and alternate with slices of sponge cake and blueberry compote and refrigerate for at least 6 hours to set.
- Just before serving, top each mousse with whipped cream and a scattering of blueberries.