1. COMBINE the chocolate, cream, milk and peanut butter in a saucepan and gently heat, stirring, until melted and smooth. Remove from the heat.
2. WHISK together the yolks and sugar until thick and sugar has dissolved. Slowly add the chocolate mixture to the egg yolks, whisking continuously until combined.
3. DIVIDE mixture between 4 x ¾ cup ramekins. Place in a baking dish; carefully pour boiling water to halfway up the sides of the ramekins and then bake in a moderately slow oven 150°C for 50 minutes or until just set. Cool on bench for 1-2 hours before refrigerating until cold.
4. SERVE topped with marshmallows and chocolate sauce.