Line an 8-inch (20cm) square tin with baking parchment, leaving some overhang so you can lift the shortbread out later. Preheat oven to 180°C (350°F).

Beat the softened butter and sugar together until light and fluffy. Add the flour and salt, mixing until it just comes together as a dough. Press evenly into the tin, smoothing the top with the back of a spoon.

Bake for 20-25 minutes until pale golden. Remove from oven and leave to cool in the tin.

In a heavy-bottomed saucepan, melt the butter, brown sugar, condensed milk, and golden syrup over medium heat. Stir constantly until the mixture begins to bubble.

Reduce heat slightly and cook for 6-8 minutes, stirring all the time, until the caramel thickens and darkens slightly. Stir in a pinch of salt, then pour over the cooled shortbread. Smooth with a spatula and leave to set at room temperature for about 1 hour.

Melt the white chocolate gently (either in a heatproof bowl over a pan of simmering water or in short bursts in the microwave). Pour over the caramel and smooth the top. Tap the tin lightly to remove any air bubbles.

Leave to set completely at room temperature (or chill for faster results, but note the chocolate may crack more easily when cutting).

Once fully set, lift out of the tin and slice into squares using a sharp knife. Wipe the knife clean between cuts for neat edges.