For the orange butter sauce: 

1. Boil orange juice for 5 minutes or until reduced in half. 
2. Add butter and stir until melted. Remove from heat. 

For the orange biscuits: 

1. Preheat oven to 425 degrees F. 
2. Use your fingers to rub sugar and zest together until the sugar is moistened and looks like wet sand. 
3. Whisk together orange sugar, flour, baking powder, and salt in a large bowl. 
4. Cut in shortening using two forks or a pastry blender until it is the size of small peas. 
5. Combine milk and orange juice then stir in to flour mixture. It will make a sticky dough. 
6. Turn out dough onto a well-floured work surface. Sprinkle the top with flour and knead about six times with folding dough over in half and using more flour as needed. 
7. Pat dough out to 3/4-inch thickness. Cut out biscuits with a round cutter, by dipping the cutter in flour then pressing the cutter into the dough. Do not turn cutter while pressing. 
8. Place cut out biscuits close together but not touching on a baking sheet. 
9. Gather dough scraps and fold 2 or 3 times, pat out again, and cut biscuits. Repeat until dough is used up. 
10. Brush tops with orange butter sauce. 
11. Bake for 15 to 20 minutes, or until lightly browned. 
12. Serve warm or at room temperature with remaining sauce.