Peel and coarsely chop the sweet potatoes. Cover with water and bring to a boil in a large pot. Salt the water and cook the sweet potatoes until tender, 8 to 10 minutes. Drain and return the sweet potatoes to the hot pot. Mash the potatoes with the stock and butter. Add in the orange juice and 2 tablespoons of the orange zest. Then add in the thyme, paprika, cinnamon and some pepper. Taste and adjust the seasoning. Cover and remove from the heat and serve immediately. To keep warm, create a water bath by placing the pot of mashed potatoes in 1 inch gently simmering water in larger pot or deep skillet.