Place the sweet potatoes chunks in a large pot and cover with a couple inches of cold water. Add the sald and bring to a boil. Boil for 7-10 minutes, or until you can just starting to get tender, but not fully cooked. Drain and set aside.
Mix the remaining ingredients in a large sauté pan and bring to a boil on high heat. Cook until sauce reduces to a syrup.
Preheat oven to 400 degrees F.
Add sweet potatoes to a large lightly buttered casserole dish, add the sauce, toss gentle to combine.
Bake until the sauce reduces to a syrup and the potatoes are tender, about 10-15 minutes. Serve hot.
Garnish with a bit of orange zest and some rosemary.