Stir together first 3 ingredients in a 1-cup glass measuring cup; let stand 5 minutes.
Combine flour and next 3 ingredients in a large mixing bowl; cut in shortening with a pastry blender until crumbly. Gradually add yeast mixture and buttermilk, stirring just until dry ingredients are moistened. Stir in cranberries and chopped walnuts. Cover and chill at least 1 hour or up to 48 hours.
Turn dough out onto a lightly floured surface; knead 3 or 4 times. Pat to 1/2-inch thickness. Cut dough with a 2-inch round cutter; place on ungreased baking sheets.
Bake at 450° for 10 minutes or until golden. Serve hot with Mock Devonshire Cream and, if desired, jelly.
NOTE: For testing purposes only, we used Ocean Spray Craisins for sweetened dried cranberries.