Bring A Large Pot (5-Quart), Half Filled With Water, To A Boil. Add The Oxtails. Parboil For 30 Minutes. Drain The Pot. Rinse The Oxtails In Water. Trim The Oxtails Of Any Excess Fat. 2 Return The Oxtails To The Pot. Cover With Water By An Inch. Add The Orange Peel, Star Anise, Ginger, And Salt. Bring To A Boil, Reduce To A Simmer. Cover And Let Simmer For One Hour. Add The Peanuts And Simmer For 2-3 More Hours, Until The Oxtail Meat Is Tender And Falling Off The Bone. 3 At The Point, You Can Either Skim The Fat Off The Soup And Proceed To The Next Step, Or Let The Soup Cool, And Chill It Overnight In The Refrigerator. The Next Day The Fat Will Have Solidified And Will Be Easy To Pull Up From The Top Of The Soup. The Flavors Will Also Have Had More Of A Chance To Blend And Be Absorbed By The Oxtails If You Let The Soup Sit Overnight. 4 Bring Soup To A Simmer. Add The Chili Pepper Flakes And Mustard Greens. Cook For 5 More Minutes, Or Until The Mustard Greens Are Tender. Serve With Garnishes Of Chopped Fresh Cilantro, Green Onions, And Freshly Grated Ginger.