Cook Beef In Water With Salt For 1 Hour Or Until Beef Is Soft. Remove Beef And Reserve Broth. Shred The Beef Into Threads And Set Aside. Simmer The Onion, Garlic, Tomato, Tomatillos, Bread Crumbs, Chile And Achiote In 2 Cups Broth Over Moderate Heat For 10 Minutes. Cook The Mixture Somewhat And Process Into A Smooth Paste. Add 2 Cups Broth To The Sauce And Simmer The Mixture Over Low Heat For 10 Minutes To Thicken. Add Potatoes And Beef And Simmer For 20 Minutes Or Until Potatoes Are Soft. Serve Warm With Tortillas Or Rice.