Add the heavy cream, milk, cocoa powder, and sugar to a medium sized sauce pan and heat through over medium high heat until the sugar is dissolved. Whisk everything together as it heats.
Add the chopped chocolate to a medium sized bowl. Pour the cream mixture over the top of the chocolate and let it sit for about 1 minute. Whisk it all together until the chocolate is melted and can be stirred in completely.
Stir in the vanilla extract and salt.
Place the mixture in the fridge for at least 2 hours, up to 24 hours.
Pour the mixture into a 2QT sized ice cream maker, and let the ice cream maker run according to the manufactures directions, or until the ice cream is churned into a thick soft serve ice cream.
Microwave the peanut butter for 30 seconds, until it is nice and runny.
Scoop about 1/3 of the ice cream into a 2 QT container, then drizzle about 1/3 of the peanut butter over the top of the ice cream.
Repeat with more ice cream, more peanut butter, more ice cream, and more peanut butter.
Cover the ice cream and place it in the freezer for 6 hours, or overnight, for a thicker, harder, hand scooped ice cream.