1. To make the double chocolate pudding, in a medium saucepan, whisk together the cocoa powder, 3/4 cup plus 2 tablespoons of sugar, corn starch, and salt.
2. Gradually whisk in 1 cup (250ml) of the milk, stirring until it’s lump-free. Mix in the rest of the milk, as well as the egg yolks and cook the mixture over moderate heat, stirring constantly with the whisk, until the mixture starts to boil and thickens enough to coat the back of a spoon.
3. Once it starts to thicken, reduce the heat if necessary to keep the mixture at a very low boil, stirring constantly with the whisk or a heatproof spatula until the pudding is thick and holds its shape, about 2 minutes. Remove from heat and scatter the chocolate over the top. Stir the chocolate in with a heatproof spatula, along with the vanilla, until the chocolate is fully melted and the mixture is smooth.
4. Divide the mixture into 4 or 6 glasses or bowls, and chill for at least two hours. Cover the tops if you wish to avoid a skin forming on the surface. (Which is my favorite part, but some don’t like it.)
If the mixture seems lumpy before you scrape it into the glasses, give it a couple of brisk stirs with a whisk, or press it through a mesh strainer to smooth it out.
5. To make the cocoa nib brittle, lightly oil a 12-inch (30cm) area on a baking sheet. Set aside.
6. Spread the 1/4 cup of sugar in a skillet, in an even layer. Heat over medium heat until the edges liquify, then begin to turn an amber color. Using a heatproof spatula, or other utensil, gently stir the liquified sugar in toward the center, stirring the mixture as gently as possible until the liquified sugar is a dark amber color and just begins to smoke.
7. Remove from heat and immediately stir in the cocoa nibs, just enough to that they are coated with the caramel. Scrape them onto the oiled part of the prepared baking sheet and spread as best you can, before it hardens. (If it gets too cool in the pan, you can rewarm the caramel with the nibs slightly over low heat, to make it spreadable.) Let the brittle harden at room temperature. When cool, crumble into little bits.