In a large bowl, combine flour, baking powder, sugar and salt. Cut in butter until well combined.
In a smaller bowl, mix together the cream, vanilla extract and egg.
Add the cream mixture to the dry ingredients, and then stir in the blueberries and lemon zest.
Roll the dough on to a floured surface and cut into biscuit-sized rounds. Alternately, you can also divide the dough into 12 pieces, roll each piece into a ball in your hands, and flatten on to a baking sheet to speed up the process.
Bake on a parchment paper lined baking sheet for 15-17 minutes or until lightly golden brown. Allow to cool slightly.
Combine all of the ingredients for the lemon glaze, adding water 1/2 tsp. at a time if necessary to thin the glaze. Drizzle over the warm scones.