Warm the milk in a saucepan over medium-low heat, stirring occasionally. Remove from heat when it just starts to bubble around the edges. Don’t bring to a full boil.
Off heat, add the chopped chocolate. Whisk until fully melted and smooth.
Pour into mugs and top with peanut butter whipped cream if desired.
Peanut Butter Whipped Cream (optional)
Whisk the peanut butter in a mixing bowl on its own for a few seconds to loosen it up slightly.
Add the heavy cream, powdered sugar, and vanilla.
Beat on medium-high with a hand or stand mixer for about 2 minutes, until soft-to-medium peaks form. Watch it near the end as overbeating turns it grainy.