Grate hard butter and place in freezer. Freeze blueberries. Whisk liquid with sour cream and vanilla. Refrigerate until needed. In a large bowl whisk flour, sugar, 2 t baking powder, 1/4 t baking soda, lemon zest, salt (put through sifter). Add grated butter to flour mixture and mix gently with hands. Fold in sour cream mixture. DO NOT OVERMIX. Turn dough onto well floured surface and knead dough 6-8 times....being gentle. It should just hold together in a raggedy ball. It is a soft/wet dough. It will stick as you knead, so add a bit of flour to prevent it from sticking. Use bench scraper to help lift dough. Roll dough out in a 12" square. Fold the top and bottom of the dough over the center (use bench scraper). Fold sides of the dough over to form a 4" square. Chill the dough in the freezer for about 5 minutes.
Flour countertop again. Roll the chilled dough again in a 12" square. Sprinkle with nuts (optional) and the chilled blueberries or chocolate chips to 1/2" of edge. Roll dough in a log, jelly roll style. Turn the seam side down and press down on the log to form a 12x4 inch rectangle. Cut into 4 rectangles, cut each rectangle into two triangles. Place scones onto parchment lined baking sheet. Brush with the melted butter and sprinkle with raw sugar. Place in refrigerator for 20 minutes...keeps them from spreading out so much.
PREHEAT OVEN TO 400 DEGREES.
Bake for 15-20 minutes until golden brown. Place on wire rack to cool. Drizzle with powder sugar glaze if desired (use fork to frost). Creates a very tender and delicious scone.