Mix together the flour and salt in a bowl. Add the sugar and Yuva yeast. Mix together well and add the egg and milk.
Stir the mixture, then add the butter in small pieces and knead the dough for 10 minutes. Place the dough in a large bowl, cover with a clean towel and rest for 90 minutes.
Spread the dough out, add the blueberries and brush with a little sugared milk. Leave the dough to rest again for 30 minutes.
Sprinkle a little castor sugar over the top of the brioches and bake in a preheated oven for 15 to 20 minutes at 180°C.
