Whisk first 5 ingredients in large bowl. Whisk buttermilk, sour cream, eggs and vanilla in another large bowl. Add to dry ingredients. Stir until batter is just blended but still lumpy (do not overmix).
Melt 1/2 tablespoon butter on griddle over medium heat. Pour batter by 1/3 cupfuls onto griddle, spacing 2 inches apart. Cook until bubbles break on surface, about 3 minutes. Turn pancakes over. Cook until bottoms are golden, 3 minutes. Transfer to plates. Repeat with remaining batter, adding butter to skillet as needed.
Serve pancakes immediately with butter and Blueberry Compote.