Melt the dark chocolate in a heatproof bowl over simmering water (double boiler method). Let it cool slightly.

In a mixing bowl, whip the heavy cream with sugar until soft peaks form.

Divide the whipped cream into two portions. Gently fold the melted chocolate into one portion until smooth.

In the other portion, mix in the orange zest and a tablespoon of orange juice for a citrusy flavor.

In serving glasses, layer the chocolate cream, orange cream, and optional crushed cookies or granola. Repeat the layers until the glasses are filled.

Smooth the top and garnish with grated chocolate or additional orange zest if desired.

Chill in the refrigerator for at least 2 hours before serving.