Heat the oven to 180 C / 355 F. Line an 8x8-inch square baking tin with baking paper, leaving overhang on two sides for easy removal.

Combine the flour, caster sugar, and salt in a mixing bowl. Add the cold cubed butter and rub it in with your fingertips until the mixture resembles coarse breadcrumbs.

Press the mixture firmly and evenly into the base of the prepared tin. Use the back of a spoon to compact it.

Bake for 18 to 20 minutes until pale golden at the edges. Remove from the oven and set aside to cool slightly.

Steep the 3 Earl Grey tea bags in 3 tbsp of boiling water for 5 minutes. Squeeze out the bags and discard. You should have about 2 tbsp of very strong tea liquid.

Combine the condensed milk, butter, golden syrup, brown sugar, and salt in a medium heavy-bottomed saucepan over medium-low heat. Stir constantly until the butter melts and the sugar dissolves.

Add the brewed tea liquid and continue stirring. Cook for 10 to 12 minutes, stirring constantly, until the caramel deepens to a warm amber and pulls away cleanly from the sides of the pan.

Remove from heat and let the caramel sit for 15 minutes until it is warm but not steaming.

Pour the caramel evenly over the shortbread base. Smooth the top with the back of a spoon. Leave to cool at room temperature for 30 minutes, then refrigerate for 1 hour until firm.

Melt the chopped dark chocolate and 15 g butter together in a heatproof bowl set over a pan of barely simmering water. Stir until smooth and glossy.

Pour the melted chocolate over the set caramel layer. Tilt the tin gently to spread it to the edges.

While the chocolate is still slightly soft, score it into 16 bars with a sharp knife dipped in hot water. This prevents cracking later.

Refrigerate for at least 30 minutes until the chocolate is fully set. Use the baking paper overhang to lift the slab out, then cut along the scored lines with a sharp knife.