The night before: Grate the frozen butter with a cheese grater (large holes) and return to freezer. Combine sour cream and milk, return to refrigerator. Combine dry ingredients and refrigerate. If you are using fresh berries, lay them on a sheet pan and freeze. Next morning (at least 60 minutes before serving): Preheat oven to 400. Combine butter and dry ingredients thoroughly. Add milk/sour cream mixture, Mix until dough comes together. Turn out on floured work surface. Knead lightly. Return dough to bowl and refrigerate. 30 minutes before serving: Turn out onto floured work surface. Roll dough into a rectangle approximately 12x18. Distribute berries evenly over the dough and press into dough. Using a scraper, fold up the dough into an 18 inch log. Flatten slightly. Paint with egg wash and sprinkle with raw sugar. Cut into triangles and place on greased or non-stick sheet pan. Bake 12-15 minutes.