1. Preheat the oven to 180 °C.
2. Grease 12 large dariole moulds or ramekins (8 cm).
3. In a double boiler, melt the chocolate and butter together until smooth. Remove from the heat and stir in the chilli flakes and then the egg yolks and flour.
4. In the bowl of an electric mixer, with the whisk attachment, beat the eggs and sugar together until light and fluffy. Fold the egg mixture into the chocolate mixture.
5. Bake for 10 minutes. (Do not feel tempted to leave in longer as this one sets outside the oven.) Let stand for 5 minutes. Gently run a knife around the edge of each cake and remove each one.
As the cakes have a soft centre, remember to place them flat on their bottoms. Serve warm.
Optional: Decorate with melted chocolate and fresh chillies.