You can really add whatever you want. I used:
100g condensed milk
200g plain chocolate
2 tbsp golden syrup
50g small marshmallows
8 crumbled digestive biscuits
Handfuls of sultanas, mixed peel and chopped glace cherries. Add as much as you like until you get a nice consistency.
Sorry it isn't an exact science but as I said it is a really adaptable recipe.
We will be using the rest of the condensed milk in peppermint creams so wrap it up and stick it in the fridge ready to use.