In a saucepan, combine the double cream, dark and milk chocolate, peanut butter and golden syrup until everything has melted together.
In a sundae glass or bowl, put a scoop of ice cream, followed by some of the chocolate sauce and the dulce de leche. Continue to build your sundae with the mini marshmallows and the bashed up peanuts.
Finish with the chocolate sauce and top with the smashed peanuts.