1. In a medium saucepan, combine the cocoa powder, sugar, and salt. Add about one-quarter cup of the measured milk, whisking vigorously until a smooth, thick paste forms.

2. Pour the remaining milk into the saucepan with the paste. Place over medium heat, stirring constantly until the mixture is warmed and small bubbles just begin to form around the edges (do not boil).

3. Remove the pan from the heat. Add the finely chopped chocolate and let it sit for sixty seconds, then whisk until the chocolate is completely dissolved and the mixture is uniform.

4. Return the pan to very low heat. Add the creamy peanut butter and whisk steadily until it is completely melted and fully incorporated into the chocolate base.

5. Stir in the vanilla extract. Taste and adjust the sweetness if necessary.

6. Pour immediately into mugs, optionally straining through a fine-mesh sieve for a silky finish, and serve with desired toppings.