In a large bowl, combine the first six ingredients. Cut in shortening until mixture resembles coarse crumbs. In a small bowl, combine sour cream and egg; add to dry ingredients just until moistened. Turn onto a lightly floured surface; knead 8-10 times.
Pat or roll out to 1/2-in. thickness; cut with a floured 2-1/2-in. biscuit cutter. Place 2 in. apart on a greased baking sheet. Brush with butter. Bake at 425° for 8-12 minutes or until golden brown. Serve warm.