Preheat your oven to 220°C (200°C fan) and line a baking tray with parchment paper. The high heat is essential — you want the butter to melt quickly and create steam, which gives scones their lift. You should hear the oven click as it reaches temperature.

In a large bowl, whisk together the flour, sugar, baking powder, and salt. The mixture should look pale and uniform, with no lumps of sugar or streaks of salt. The flour will smell dry and clean.

Add the cold butter cubes to the flour mixture. Using your fingertips, rub the butter into the flour until the mixture resembles coarse breadcrumbs. You'll see small, pea-sized butter pieces remaining — that's perfect. The texture should feel sandy but with visible butter flecks throughout.

In a separate small bowl, whisk together the double cream, egg, and vanilla extract until the mixture is smooth and pale yellow. If using yogurt, whisk it in here. The liquid should be well combined with no streaks of egg white.

Pour the wet ingredients into the dry ingredients and stir gently with a fork until a shaggy dough forms. Do not overmix — you want it to look rough and uneven. Add the blueberries and fold them in with just three or four turns. The dough should feel soft but not sticky.

Tip the dough onto a lightly floured surface and bring it together with your hands into a rough rectangle about 2cm thick. You'll see small berry patches and butter pockets — that's exactly what you want. The dough should feel cool to the touch.

Cut the dough into 8 triangles using a sharp knife or bench scraper — do not twist the cutter if using a round cutter, as that seals the edges. Place them on the prepared baking tray, spacing them about 3cm apart. The scones should look rustic and slightly irregular.

Sprinkle the tops with demerara sugar and bake for 14–16 minutes. After 10 minutes, check the colour — the scones should be golden brown on top and slightly darker at the edges. When done, they will feel firm to a gentle touch and smell nutty and buttery. A skewer inserted into the centre should come out clean.

Transfer the scones to a wire rack and let them cool for 5 minutes before serving. They will release a faint steam as they cool. The tops should be crisp, and the insides soft and tender when you break one open.