Line the base and sides of a 18cm x 28cm rectangular slice tray with baking paper.
Place the white chocolate and coconut oil into a heatproof, microwave-safe bowl.
Heat, uncovered, on 50% power, stirring every minute with a metal spoon, for 4-5 minutes or until the chocolate and coconut oil melts (if using a Thermomix, melt for 3-4 minutes, 80 degrees, Speed 2).
Remove from the microwave and stir until smooth.
Stir through the coconut, marshmallows, Turkish Delight and pistachios.
Spread the mixture into the prepared baking tray and place in the fridge for 2 hours or until completely set.
Use a sharp knife to cut into slices (if you are having trouble cutting the slice, run your knife under hot water and then dry completely before cutting - the heat will help to cut the slice evenly).