Preheat the oven to Gas Mark 3, 170°C, fan 150°C. Mix all the ingredients in a blender until they come together. Scoop out the dough and press into a 20cm (8in) fluted tart tin. Chill for 2 hours to firm.
Put in the oven and bake for 15 minutes. Remove and lightly prick all over with a skewer. Cut into 8 triangles and sprinkle with more sugar. Return to the oven for 10-15 minutes until golden and sandy to the touch. Allow to cool in the tin.
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Freezing and defrosting guidelines
This recipe can be frozen, after chilling it in the refrigerator for 2 hours (before the baking stage), and kept in the freezer for up to three months. Always defrost and heat thoroughly before eating.