Chop the chocolate and melt it with the butter over a hot water bath. Beat eggs, sugar and cinnamon until frothy. Add the chocolate mixture. Mix the flour and cocoa and stir in briefly. Fill into a mold (approx. 20 x 30 cm) lined with baking paper and bake in a hot oven at 180 ° C (HL 160 ° C) for approx. 30 minutes until the surface is crispy but the inside is still a bit soft. Let cool in the tin, cut into cubes.