Chocolate Custard Cake

Step 1: Turn the base of a 20 cm (8-inch) springform pan upside down so the finished cake can slide off without catching on the lip. Grease the base with butter, press a square of baking paper onto it, then clip the pan sides in place with the excess paper extending beyond the edge.

Step 2: Preheat the oven to 180°C (350°F), or 160°C fan-forced.

Step 3: In a large saucepan, heat the milk, vanilla, and about half the sugar over medium-high heat, stirring to dissolve the sugar. Heat until just before boiling.

Step 4: In a large bowl, whisk the egg yolks with the remaining sugar. Add the cornflour and whisk until smooth.

Step 5: While whisking the egg mixture, slowly pour in the hot milk in a thin stream. Whisk until fully combined.

Step 6: Pour the egg-and-milk mixture back into the saucepan. Cook over medium-low heat, stirring constantly so the base does not catch, until the custard starts to thicken, about 3 to 5 minutes. If it becomes lumpy, take the pan off the heat and whisk vigorously until smooth.

Step 7: When the custard is thick and steamy and the first large bubbles appear on the base, whisk constantly on the stove for another 45 seconds, then remove from the heat.

Step 8: Add the chopped chocolate and stir until it has fully melted.

Step 9: Transfer the custard to a bowl and immediately cover it with plastic wrap touching the surface. Strain it if you are concerned about lumps. Set aside while you prepare the base.

Step 10: Break the cookies into pieces by hand and put them in a food processor. Process to fine crumbs, add the melted butter, then process again until combined.

Step 11: Transfer the crumbs to the prepared pan and press them evenly and firmly over the base.

Step 12: Whisk the custard until smooth and loosened, then pour it over the base and smooth the surface. Bake for 60 minutes, rotating the pan after 45 minutes. The cake will still wobble when you take it out of the oven.

Step 13: Leave the cake to cool in the pan on the counter for 3 hours. Refrigerate it for at least 12 hours so the custard can fully set.

Step 14: For neat slices, cut the cake while cold from the refrigerator and serve at room temperature for a creamier texture. Remove the springform sides and baking paper, then use the paper overhang to slide the cake off the base. Cut into slices and serve with Chantilly cream and raspberries or strawberries, if desired. Dust with icing sugar.