This is a variant on lemon surprise pudding, in which the mixture divides on cooking to produce a sponge above the thick lemony sauce which forms below. Indeed, it is known in my house as Lemon Surprise Pudding, the surprise being that it's chocolate. Although I didn't actually eat this as a child, it is heady with reminders of childhood foods: the hazelnuts in the sponge bring back memories of Nutella, the thick, dark, fudgy sauce of chocolate spread. The proportions below are geared towards 6, but easily feed 8. It's heavenly with fridge-cold heavy cream poured over it. It is also child's play to make. Choose good cocoa and good chocolate and stick carefully to the exact measurements. (You can, though, use 1 2/3 cups flour in place of the 1 1/4 cups flour and 1/2 cup ground nuts, if you prefer increasing the amount of baking powder needed to 1 1/2 teaspoons.) Use one of those standard white soufflé dishes 8 inches in diameter, or a shallow square 12-inch pan. If you've got only a single oven, it makes sense to use the shallow dish: it will take less time to cook.