Mary Berry shows how to make swirling chocolate and orange custard tart on The Great British Bake Off Masterclass 3 in 2014.

Mary’s tart is a swirl of light and dark chocolate in a thin pastry case.

This dessert proved to be one of the most complicated technical challenge of the series for the bakers in the tent to get to grips with.

The ingredients for the pastry: 100g plain flour, plus extra for dusting, 50g icing sugar, 50g unsalted butter, diced, 1 large egg yolk and 1 tablespoon cold water.

For the chocolate filling 75g unsalted butter, 115g dark chocolate (no more than 60% cocoa solids), finely chopped, 115g golden caster sugar, 55g plain flour and 4 medium eggs.

For the orange filling: 25g unsalted butter, 50g white chocolate, finely chopped, grated zest of 1 orange, 35g golden caster sugar, 25g plain flour, 2 medium egg yolks and 1 x 23cm round, fluted tart tin, greased with butter; a baking sheet.