Line a cookie sheet with parchment paper. Set aside. Combine the chocolate, peanuts and peanut butter into a slow cooker.
Cover and cook on low for 1 hour. Remove lid and stir until smooth. Turn off the slow cooker and allow chocolate to cool for 2 minutes and then stir in marshmallows.
Immediately place rounded spoonful's onto the lined cookie sheet. Top with extra marshmallows and chopped peanuts if desired. Allow to cool.
Variation: You can omit the chocolate chunks and use 1 3/4 cup semi-sweet chocolate chips if desired.Storage: Store in a covered container in the refrigerator for up to 1 month or in the freezer for 3 months.