Classic French Chocolate Mousse

Melt the bittersweet chocolate and butter together in a heatproof bowl over simmering water, stirring until smooth. Remove from heat and let cool slightly.

In a separate bowl, whisk the egg yolks with 2 tablespoons of sugar until pale and thick. Stir in the vanilla extract and espresso powder, if using.

Gently fold the melted chocolate into the egg yolk mixture until well combined.

In a clean bowl, beat the egg whites with a pinch of salt until soft peaks form. Gradually add the remaining tablespoon of sugar and continue beating until stiff peaks form.

In another bowl, whip the heavy cream until soft peaks form.

Carefully fold the whipped cream into the chocolate mixture, followed by the beaten egg whites, in two additions each, until just combined and airy.

Spoon the mousse into serving glasses, layering with chocolate cookie or cake crumbs.

Chill for at least 2 hours, or until set.

Before serving, garnish with dark chocolate shavings and an extra sprinkle of crumbs.