Preheat the oven to 400°F (207°C). Mix the Egg Wash ingredients together, set aside.
Put your butter, flour, baking powder, sugar and a pinch of salt into a mixing bowl and use your thumbs and forefingers to break up the butter and rub it into the flour, so you get little cornflake–sized pieces.
Make a well in the middle of the dough, add the eggs and milk, and stir it up with a spatula. Add the blueberries to the mixture. Add a tiny splash of milk if needed, until you have a soft, dry dough.
Move it around as little as possible to get it looking like a scruffy mass – at this point, you're done. Sprinkle over some flour, cover the bowl and pop it into the fridge for 15 minutes.
Roll the dough out on a lightly floured surface until it's about 1-inch (2.5cm) thick. With a 2 1/2-inch (6cm) round cutter, cut out circles from the dough and place them upside down on a baking sheet – they will rise better that way. Re-roll any off cuts to use up the dough.
Brush the top of each scone with the Egg Wash twice and bake in the oven for 15-18 minutes, or until risen and golden. At that point, take them out of the oven and leave them to cool down a little. Serve with clotted cream (preferred), fruit jam, lemon curd, or butter.