Combine cornstarch, sugar, cocoa powder, kosher salt, and instant coffee granules (if using) in a dry, heavy-bottomed 2-quart saucepan. Try to smash any clumps of cornstarch or cocoa powder in the pan to prevent lumps in the final product.

Drizzle about 1/2 cup of the milk into the pan while whisking. Whisk until you have a smooth thick mixture. Continue slowly adding the milk to the pan, whisking constantly, until all the milk has been incorporated and the mixture is smooth. Turn the heat to medium and bring to a boil, whisking constantly to prevent scorching or clumping. Boil for 2 minutes, still whisking constantly. Remove the pan from the heat and add the chopped chocolate and extracts. Whisk slowly but constantly until the chocolate has melted and fully incorporated into the hot pudding. You will be able to tell it done when the colour darkens and it becomes glossier looking. Pour immediately into dessert cups or jelly jars. You can serve the pudding hot, as is, or lay a piece of plastic directly on the surface of the pudding and transfer the cups carefully to the refrigerator (they will be hot!). Chill for at least 2 hours.

Serve with a generous dollop of whipped cream and a little grated chocolate, if desired.