Preheat oven to 375 degrees F. Combine first 8 ingredients in bowl of a food processor (be careful not to overprocess). Add butter in tablespoon-size pieces, and process until mixture is crumbly and no large pieces of butter remain. Add 1 cup of milk until dough comes together. Turn dough out onto well-floured surface. Knead dough gently for 10 to 12 strokes or until nearly smooth. Roll or pat dough to ½- to ¾-inch thickness, and cut with 3-inch cutter.
Place scones on greased baking sheet. Knead scraps together gently, reroll, and cut until dough is used up. Combine egg yolk and 2 tablespoons milk. Brush scones with egg mixture; sprinkle them lightly with sugar. Bake for 15 minutes or until scones are firm and golden brown.
Tip: If you don’t have a food processor, stir together the first 8 ingredients in a large bowl. Cut in butter until mixture resembles coarse crumbs. Make a well in the center. Add 1 cup milk all at once. Stir just until dough clings together. Continue as directed above.