Stir together flour and mustard; cut in shortening with a pastry blender until mixture is crumbly. Stir in cheese. Add buttermilk, stirring until dry ingredients are moistened. Turn dough out onto a lightly floured surface, and knead 3 or 4 times.
Roll dough to 3/4" thickness; cut with a 2" biscuit cutter. Place biscuits on a lightly greased baking sheet.
Bake at 450° for 10 to 12 minutes or until lightly browned.