Preheat your oven to 220ºc/200ºfan, and place a lined tray in the oven to preheat.
Tip the self-raising flour, sea salt, baking powder, and cold and cubed unsalted butter into a food processor and pulse until the mixture resembles bread crumbs.
Pour the mixture into a large bowl, and stir in the caster sugar.
Alternatively, you can cut the cold butter into small cubes, and rub the mixture together between your fingers to get the breadcrumb texture if you don't have a food processor
Add the lemon juice and lemon zest in.
Heat the full-fat milk in the microwave or on the hob so it becomes warm, but not hot. I usually heat it for about 30-40 seconds in the microwave.
Add the milk into the rest of the mixture, and stir with a spatula as it'll be very wet at first.
Make sure the dough is mixed well, and add in the blueberries. Carefully mix together.
Sprinkle some extra flour onto the work surface, and turn the dough out onto it and gently roll it out, or press it down, to be about 4/5cm thick.
Using a 5cm cutter, cut out the scones - you'll have to re-roll the mixture a couple of times to get them all out of the mix.
Take the tray out of the oven, and put the scones onto it. Brush the top of the Scones with the beaten egg mixture and bake in the oven for 10 minutes.
Leave to cool for at least 10 minutes once they're out so you don't burn yourself. And then, enjoy!
Notes
You can add the zest of two lemons to make them even more lemon flavoured if you wish!
You could easily make smaller or bigger scones if you wanted, but adjust the baking times accordingly.
These are best on the day of baking, but they will last for two days after.
I have tried these with frozen blueberries, and in my opinion it doesn't work. They produce too much liquid and ruin the scones.
You could swap the fruit for others, but beware blueberries are quite small and everything else is larger. Keep to the same amount, but chop up the fruit so they're not too big.
I served mine with a dollop of Rodda's clotted cream, and homemade lemon curd.