Preheat the barbecue for indirect cooking for 10 minutes. (please refer to your handbook, supplied with your barbecue)
Place the butter and sugar in a medium sized bowl and beat until pale and creamy. Stir in the flour and mix until soft a dough forms.
Press the dough into the bottom of the Q ware, or a shallow baking dish.
Bake the base in the barbecue for 10 minutes or until lightly browned.
While the base is baking, mix the condensed milk, coconut, cranberries, cherries, pistachios and in a medium sized bowl.
Once the base is cooked, gently spread over the condensed milk mixture. Continue to cook the slice for a further 10 minutes.
After the 10 minutes, gently push the marshmallows into the slice. Continue to cook the slice for a further 5 minutes.
Remove the slice from the barbecue and set aside to cool.
Melt the baking chocolate in a microwave. Spread the melted chocolate over the slice. Leave the slice overnight to set completely.
Once set cut into squares and store in the fridge.