With an electric whisk beat the eggs with the sugar, then add the flour and mix well with a whisk by hand. Melt the chocolate in a bain-marie with butter and add to the mixture of eggs, flour and sugar. Mix and pour into a cake tin.
Cook the cake in a preheated oven at 180ºC for about 25 minutes (it should not dry inside).
Cool it in the blast chiller with the function of blast chilling for about twenty minutes, serve it with a dusted with powdered sugar.