Preheat oven to hot (425°). Lightly grease 1 small or 2 large cookie sheets. Stir together flour, sugar, baking powder, baking soda and salt in large bowl until well mixed. Cut in butter with pastry blender until mixture resembles coarse meal. Stir in currants. Beat egg in small bowl; remove and reserve 1 tablespoon. Stir in yogurt until blended. Pour all at once into flour mixture. Gently mix together with spoon until flour is moistened. Turn out onto lightly floured surface; shape into ball. Cut in half. Pat out each half into a 7-inch circle. Transfer to prepared cookie sheet. Cut each circle into 6 wedges. Brush top with reserved egg. Bake in preheated hot oven (425°) for 12 to 14 minutes or until golden brown on top. Serve warm. Nutrient Value Per Scone: 172 calories, 4 g protein, 5 g fat, 281 g carbohydrate, 251 mg sodium, 29 mg cholesterol. Exchanges: 1-3/4 starch/bread, 1 fat.