Adjust oven rack to middle position and heat oven to 450 degrees. Slice 8 Tablespoons of butter into 1/4" cubes and chill.
Pulse flours, baking powder, baking soda, sugar and salt in a food processor with steel blade. Mix chilled butter cubes into dry ingredients until mixture resembles coarse meal with a few slightly larger butter lumps.
Pulse in yogurt until dogh gathers into moist clumps. Remove from bowl and form into a rough ball.
With lightly floured hands, divide dough into 12 equal portions. lightly pat a portion of dough back and forth a few times between floured hands to make a ball. Place dough rounds 1 inch apart on ungreased cookie sheet. Brush dough tops with melted butter. Bake until tops are light brown 10-12 minutes. Serve immediately.