01 -
If you want the microwave route, chuck cocoa, sugar, and water in a mug and zap it for 15 seconds. Stir, throw in the peanut butter, mix again, add milk, microwave until steaming, and give it one last stir.
02 -
To make peanut butter sauce, just combine 2 tablespoons corn syrup with 1 tablespoon peanut butter in a microwave-safe dish. Heat for 10β20 seconds, wait for the bubbles, then stir until it's totally smooth.