Photograph: Martin Poole
Preheat the oven to 200°C, fan 180°C, gas 6.
Sift the flour, cream of tartar, bicarbonate of soda, 1 tablespoon of the sugar and a pinch of salt into a large mixing bowl. Add the cold, diced butter and rub it into the dry ingredients using your fingertips until the mixture resembles fine crumbs. Add the lime zest, blueberries and the 25g of desiccated coconut.
Add the lime juice to a measuring jug with the cream and milk, then stir to mix. Gradually add to the dry ingredients, mixing with a round-bladed knife until just combined. Turn the dough out on to a lightly floured surface and knead very gently and briefly, just enough to bring the dough together. Don't overwork the dough, as this will make the scones heavy.
Shape the dough into a rectangle about 2-3cm thick, and cut the scones by hand or using a 6cm round cutter. Transfer to a baking tray lined with baking paper. Brush the tops of the scones with a little beaten egg yolk. Mix the remaining sugar and coconut together, then sprinkle on top. Bake in the oven for 14-16 minutes until risen and golden.
Leave to cool before serving. Serve warm or cold with clotted cream and blueberry jam.
Kitchen secret: put a small dish of hot water in the bottom of the oven during baking – the steam will give a great rise to your scones.