Add the butter, chocolate and cream to a pan. Cook over a very low heat, stirring constantly, until fully melted, smooth, and well combined.
Distribute half of the chocolate mixture between 8 small pots or ramekins. Add a small dollop of peanut butter to each pot, then top with the remaining chocolate mixture.
Place the chocolate pots in the fridge for at least a few hours, or until completely set (they last a few days in the fridge, so they can be made in advance).
Serve topped with a few chopped peanuts, if desired.