I think the Delia one can seem a bit cocoa-powder-y rather than chocolatey, iirc. The Nigella Lawson one has chocolate in it too:
Pudding:
1 1/4 cups all-purpose flour
1 teaspoon baking powder
pinch salt
1/4 cup good unsweetened cocoa powder
1/2 cup ground hazelnuts
1 2/3 cups confectioners sugar
2 1/2 ounces best semisweet chocolate chopped roughly or chocolate morsels
2 tablespoons unsalted butter, melted
1 egg
3/4 cup milk
1 teaspoon pure vanilla extract
Sauce:
1 cup dark brown or dark muscovado sugar
1 1/4 cups unsweetened cocoa powder
Preparation: Preheat the oven to 350°.
Sift the flour, baking powder, salt and cocoa into a bowl, stir in the hazelnuts and the sugar, then add the chocolate. Whisk together the melted butter, egg, milk and vanilla and pour into the dry ingredients. Stir well, so it's all thoroughly mixed, then spoon into the buttered dish.
Now for the sauce, not that you make it yourself (the cooking does that for you) but you have to get the ingredients together. Bring 2 1/2 cups of water to a boil. Mix the brown sugar and cocoa and sprinkle over the top of the pudding mixture in the dish. Pour the boiled water up to the 2 cup mark of a measuring cup, then pour over the pudding. Put the water-drenched pudding directly into the oven and leave it there for about 50 minutes.
Don't open the door until a good 45 minutes have passed and then press: if it feels fairly firm and springy to the touch, it's ready. If you're using the shallow dish, it'll be ready in 35-40 minutes.
Remove from the oven and serve immediately, spooning from the dish and making sure everyone gets both sauce and sponge.