Rub the cold, cubed butter into the flour and salt with your fingertips until the mixture looks like coarse breadcrumbs.

Add the cold water 1 tablespoon at a time, mixing with a knife, until the dough just comes together. Shape into a disk, wrap, and chill for 20 minutes.

Roll the chilled dough on a lightly floured surface to about 3 mm thick and line a 23 cm / 9-inch tart tin. Trim the edges and prick the base with a fork.

Heat the oven to 190 C / 375 F. Line the pastry with parchment paper and fill with baking beans.

Bake for 15 minutes, then remove the paper and beans. Bake for another 8 to 10 minutes until the base looks pale gold and dry to the touch. Set aside and reduce the oven to 170 C / 340 F.

Pour the chilled evaporated milk into a large mixing bowl with the dark muscovado sugar. Whisk with an electric mixer on high speed for 10 to 15 minutes until thick and pale caramel colored. It should roughly double in volume by the time you stop.

Pour the filling into the warm pastry case and smooth the top with a spatula.

Bake at 170 C / 340 F for 12 to 15 minutes, until the edges are set and the center still has a gentle wobble.

Cool the tart in the tin at room temperature for 1 hour.

Chill in the fridge for at least 1 hour, or overnight, until fully set. Slice thin and serve cold.