Spray the gold spray into the bowl while shaking gently to ensure the nuts are coated on all sides. Set aside to dry.
Make the shortbread
Preheat the oven to 200C (180C fan). Put the flour, sugar and semolina in a bowl and mix well.
Add the butter - make sure it's very cold as this will help your shortbread texture to remain light rather than dense.
Rub everything together. At first it will look like crumbs and eventually it will look like a crumbly, sticky dough.
Grease a medium roasting tray generously with butter.
Tip the shortbread crumb into it and press it down to create a smooth, level base. Prick all over with a fork to discourage the shortbread from puffing up during baking.
Bake for 25-30 minutes until firm and slightly golden. You can turn to oven off now. Leave to cool completely while you make the caramel.
Make the caramel
Put the condensed milk, sugar and butter in a large, microwave-safe bowl. Mix together.
Microwave on full for 3 minutes. Remove and whisk until evenly combined. Be very careful as the bowl and caramel will be extremely hot.
Return to the microwave for another 3 minutes. Whisk again. The caramel will look frothy and may seem split when you first begin to whisk it. Don't panic, just keep mixing and it will come together as a smooth caramel. Allow to cool to room temp before moving on to the next step.
Apply the caramel layer
Spoon the caramel over the biscuit. Spread to cover.
Pop in the fridge while you prepare the ganache (this helps the caramel to firm so that the chocolate is easier to spread on top).
Make the ganache
Put the chocolate in a large heatproof bowl.
Put the cream in a small microwave-safe bowl and microwave for 30-60 second until almost boiling. Pour the cream over the chocolate.
Whisk. At first, your chocolate mixture may look dull / murky. Keep whisking and it will come together as a smooth, glossy ganache. Set aside and allow to cool but not set.
Finish assembling your Ferrero Rocher slice
Spoon the cooled ganache over the caramel. Gently spread to the edges.
Scatter the golden hazelnut pieces on top.
Push the Ferrero Rocher into the chocolate, making sure to space them evenly.
Place in the fridge to chill until set.
Run a sharp knife all the way around the edge of the tin, right to the bottom, then turn the slice out onto a board and trim off the edges if uneven/slanted.
Slice! If you only cut into 8 slices as I did, they are of course rather large. I think of them as sharing portions - great to give as Christmas gifts. You could cut into 16 long slices by additionally slicing down the middle of each Ferrero Rocher. Alternatively, you could put 12 or 16 Ferrero Rocher on top, equally spaced when decorating and then cut into neat squares.
Ferrero Rocher slices need to be kept in an airtight container. You can simply pop your container into fridge or into the cupboard or pantry, just as long as it's kept in a cool spot away from direct sunlight. These Ferrero Rocher slices will keep for up to 5 days when stored correctly.