Peel, quarter lengthwise and cut potatoes crosswise into 1/4-inch thick slices.
Combine the sweet potatoes, 1/2 t salt, sugar, and water in a large pot.
Cover and cook over low heat, stirring occasionally until the potatoes fall apart when poked with a fork (45 - 60 minutes).
Off the heat, mash the sweet potatoes in the saucepan with a potato masher or food mill. Stir in the melted butter, half-and-half, orange juice, and orange zest with a wooden spoon until incorporated.
Season with additional orange juice, brown sugar, cinnamon, salt and pepper to taste.