Place Top’n’Fill and peanut butter together in a small non-stick saucepan, over a medium heat, stirring until well combined. Bring to the boil and remove from heat.
Pour into the tart shell and place in the refrigerator to set for at least two hours.
To make the ganache, place cream in a small saucepan over a medium heat, bring to just below boiling point. Pour over chocolate and gently stir to combine. Leave to stand for several minutes before stirring again. Repeat process until chocolate has melted, making sure mixture is not stirred too much.
Carefully spread the ganache over the top of the set caramel mixture and sprinkle over the chopped nuts. Return the tart to the fridge for at least an hour until ganache has set.