Dissolve the chocolate pudding powder in 100 ml (1/2 cup) milk.
Stir the remaining milk in a small pot with the sugar and peanut butter until smooth and bring to the boil. Reduce heat to the lowest level.
Slowly mix the pudding-powder-milk mix in the pot with the rest of the milk, stirring continuously with a whisk so that no lumps form. Stir until the pudding thickens, then remove from heat immediately.
Divide the pudding while still hot among 3-4 small bowls.
Let cool slightly, and decorate with peanuts and cinnamon.
You can serve the pudding lukewarm if you choose a cream-like texture, or let it cool completely (e.g., in the refrigerator) if you prefer a firmer consistency.