Put the oven rack in the middle and heat to 425ºF. Cut a bar of very cold butter into very small pieces and reserve in a freezer. Melt 2 tablespoons of butter from which we stayed and reserve it. Put the blueberries in the freezer until we are going to use them.
Apart stir the milk with the cream and reserve. In a large bowl mix the dry ingredients: flour, baking powder, baking soda, salt, sugar and scrape. To this place the butter in small pieces (8 tablespoons) and mix with your fingers to form a homogenous powdery mass.
Add the milk mixture and stir with the spatula. Sprinkle a surface with flour and put this paste to knead it about 8 times to form a ball, putting flour so that it does not stick.
With the roller flatten a square of 30 cms per side. Fold one third of top and bottom (both sides towards the same center) and knead again. Re-fold, half and half again. Put the pasta in the freezer for 5 minutes.
Remove from the freezer and flatten a rectangle of 30 cms on each side again, distribute the blueberries and roll up to have a tight roll. With the edge below (where the dough is joined) flatten a rectangle of 30 x 10 cm. Using a floured knife cut 4 rectangles and once again cut each of those diagonally to have 8 triangles.
With a brush varnish the triangles with melted butter and sprinkle with sugar. Bake on a baking tray for 18 to 25 minutes until golden brown. Let stand 10 minutes before serving.
