Glazed Lemon Blueberry Scones

0 Preheat your oven to 400F
1 Grease a baking sheet.
2 Mix the flour, salt, baking powder, lemon zest, and sugar in a large bowl.
3 Use a box grater to grate the frozen butter into the dry ingredients. Stir gently to cover the butter with flour.
4 Wash the berries and let dry overnight. Dust with flour.
5 Add the milk and berries and gently mix to make a soft dough.
6 Turn out onto a floured surface.
7 Pat dough (gently!) out to 3/4 inch thickness.
8 Cut into rounds with a cutter or into wedges with a knife.
9 Place the scones on the greased baking sheet.
10 Mix the egg yolk and water and brush on the tops of the scones.
11 Sprinkle with some sugar crystals, if desired.
12 Let stand for 15-20 minutes. If the kitchen is hot put them in the fridge during this time.
13 Bake for  12-15 minutes or until the tops are golden brown. 
14 Glaze while warm.
Glaze
17 Mix all glaze ingredients together until smooth. You may need a little more Confectioner's sugar or a little more lemon juice to get the right consistency.