White Mousse Cake with With Zest of Grapefrui

This is a showstopper layer cake built on a classic genoise sponge, split into four thin rectangles and filled with billowing white chocolate mousse. The mousse itself is remarkable: whipped cream folded with melted white chocolate, candied citrus peel and toasted pine nuts, all layered so every slice shows distinct stripes of filling.

The citrus element is the soul of this cake. Grapefruit, orange and lemon peel simmer together in a sugar syrup until tender, losing their bitterness while keeping their perfume. That triple-citrus punch cuts through the sweet richness of the white chocolate in a way single-citrus versions can’t match.

Shaved white chocolate curls go on the outside, frozen first so they hold their shape and don’t smear on contact with the mousse. Mexican vanilla in the sponge adds a warm, slightly spicy note that plays beautifully with the citrus.

Chef Tips

• Beat the egg yolks and sugar until genuinely ribbon stage, a proper ribbon holds shape for a few seconds when drizzled, undermixing gives a dense sponge
• Melt the white chocolate slowly over barely-simmering water, white chocolate seizes easily if it gets too hot
• Freeze the chocolate curls until completely firm before applying, soft curls tear and bleed into the mousse
• Chill the assembled cake for at least four hours before slicing, the mousse needs time to set properly between layers
• Use a hot, dry knife wiped between cuts for clean layer definition when serving

Variations

• Swap the pine nuts for toasted slivered almonds or pistachios for a different nutty profile
• Add a splash of orange liqueur to the mousse for an adult dessert lean
• Use dark chocolate curls instead of white for dramatic contrast against the pale mousse