This recipe is based on one in Breakfast, Lunch, Tea, by Rose Carrarini (Phaidon)
- Preheat the oven to 200C. Sift the flours, baking powder and sugar into a large bowl. If the butter is soft, rub it in with your fingertips; if it is hard, grate it.
- Add the zest(from ½ a lemon or orange) and blueberries. Break the egg into a measuring jug and add enough milk to make the liquid up to 200ml.
- Whisk thoroughly with a fork. Transfer 1 tablespoon of the liquid to a cup and set aside to use as a glaze.
- Pour the remaining liquid into the scone mixture and use a large fork to mix to a slightly crumbly dough that only just forms a mass. Add a little more milk if needed.
- Tip the dough out onto a lightly floured board and pat out to a 3cm thickness.
- Use a cookie cutter to cut into rounds. Transfer the scones to a baking tray lined with baking paper.
- Brush the tops with the reserved egg and milk mixture and sprinkle with sugar.
- Bake for 15-20 minutes until golden brown on top.
- Transfer the scones to a rack to cool.