For the chocolate cakes with liquid center, first melt the butter and chocolate over low heat. Beat the eggs with sugar until foamy and add the butter-chocolate mixture and mix.
Gradually stir the flour and a pinch of cinnamon into the chocolate mixture. Grease soufflé molds with butter and dust with flour (alternatively, you can use ovenproof coffee mugs).
Fill two-thirds of the cake pans with batter and bake at 180° for 10 to 12 minutes. Sprinkle with sugar or cocoa and serve warm.