First melt the chocolate and butter over the water bath. Preheat the oven to 175 ° C top / bottom heat.
Grease a wreath form and place in the refrigerator. Beat the egg white with a pinch of salt until stiff and stir in the icing sugar. Then stir in the chocolate and butter and finally fold in the flour. Fill into the wreath form (26 cm) and bake on the middle rack for 40 - 50 minutes (chopsticks test).
Remove the cake from the mold and leave to cool on a wire rack.
For the glaze, melt the couverture with the coconut oil over the water bath and cover the cake with it.