In a saucepan, combine the chopped rhubarb and sugar. Cook over medium heat for 10-15 minutes until the rhubarb is soft and tender. Let it cool completely before layering.

Place your high-quality dark chocolate in a heatproof bowl set over a pot of simmering water. Stir until melted and smooth, then let cool slightly.

In a mixing bowl, beat the chilled heavy cream with sugar (if desired) and vanilla extract until soft peaks form.

Gently fold the rosewater into the melted chocolate, then carefully fold in half of the prepared whipped cream.

Layer the rhubarb compote and chocolate mousse alternately in clear glasses, finishing with a layer of mousse on top.

Refrigerate the parfaits for at least two hours before serving.