Whisk the flour, sugar and salt in a bowl. Rub in the cold butter with your fingertips until the mix looks like coarse crumbs with a few pea-sized pieces. Stir in the ice water 1 tablespoon at a time until the dough clumps, then press it into a disc, wrap it and chill for 30 minutes.

While the dough chills, heat the oven to 190 C / 375 F (170 C fan) and grease a 12-hole tart tin with 7 cm / 2.75-inch cups using the soft butter.

Roll the chilled dough on a floured surface to 3 mm thick. Cut twelve 10 cm / 4-inch rounds, re-rolling the scraps once, and press one round into each cup.

Whisk the melted butter and brown sugar until smooth. Whisk in the eggs and vinegar, then stir in the dried fruit and walnuts.

Spoon the filling into the cases, stirring between scoops so the fruit is spread evenly. Fill each case only three-quarters full, because the sugar bubbles up as it bakes and sticks overfilled tarts to the tin.

Bake on the middle rack for 20 to 22 minutes, until the filling is puffed and dark golden with no wobble and the pastry edges are golden brown.

Cool the tarts in the tin for 15 minutes. Loosen each one with a small knife and move it to a wire rack.