In a large bowl cream the butter and sugar until pale and then stir in the condensed milk. Sift in the flour and then work into a soft dough using your hands. Mix in the chopped white chocolate.
Take a small handful of dough and flatten with your fingers. Place 2-3 blueberries into the centre of the biscuit and fold over the sides of the dough to encase the blueberries. Repeat with the remaining dough.
Place onto baking paper lined baking trays spacing well apart then bake for about 15-18 minutes or until golden brown at the edges but still a little soft.
Leave to cool slightly and set before transferring to a cake rack.