Black Butter Millionaire Shortbread

Preheat oven to 180°C (160°C fan/Gas Mark 4). Grease and line an 8x8 inch square baking tin with parchment paper, leaving an overhang.

For the shortbread base: In a large bowl, rub the cold cubed butter into the flour until it resembles breadcrumbs. Stir in the caster sugar and mashed Jersey Royal potatoes.

Press the mixture evenly into the prepared tin. Prick the base all over with a fork.

Bake for 25-30 minutes, or until golden brown. Let the shortbread cool completely in the tin.

For the caramel: In a medium saucepan, melt the butter over a low heat. Add the golden syrup and condensed milk and stir until combined.

Bring the mixture to a simmer, stirring constantly to prevent burning. Continue to simmer for 10-15 minutes, stirring frequently, until the caramel is thick and a deep golden brown. Stir in the Jersey Black Butter until evenly combined.

Pour the caramel over the cooled shortbread base and spread evenly. Let it cool completely and set in the fridge for at least 2 hours.

For the chocolate topping: Break the dark chocolate into pieces and melt in a heatproof bowl set over a pan of simmering water (or in the microwave in 30-second intervals, stirring in between), adding the teaspoon of vegetable oil for shine. Make sure the bowl doesn't touch the water.

Pour the melted chocolate over the set caramel and spread evenly. Let it set completely in the fridge.

Once the chocolate is set, remove the millionaire shortbread from the tin using the parchment paper overhang. Cut into squares and serve.