Work the ground almonds, egg white, and sugar into a paste and knead into a ball. On a sugared surface, roll out to a round large enough to line an 8-inch nonstick flan tin, 1/4-inch thick and leave to dry for 30 minutes.
Preheat the oven to 350 degrees F.
Place the rested pastry in the tin and decorate the edges with the finger and thumb technique. Line with foil (but no baking beans) and bake blind for 20 to 25 minutes. Watch carefully to avoid scorching. Leave to cool.
Melt the chocolate in a bowl set over hot water, then mix in the cream, stirring all the time to prevent splitting. Remove from the heat and, as the chocolate starts to set, beat the mixture to a light foam. Allow to cool for 1 to 2 minutes before pouring into the cooled crackling crust. Leave to set. Serve decorated with toasted almonds and yellow rose petals.