Place carrots in large cooking pot and cover with water. Bring to a boil, add onion, brown sugar and singer, reduce to a simmer, and cook covered until carrots are about half-done. Add sweet potatoes and simmer until the vegetables are done. Drain, saving cooking liquid, and place in casserole. Make following sauce: Measure out 1 cup (230 mL) liquid, and stir in 2 tablespoons (30 mL) flour, another 1/2 teaspoon (3 mL) powdered ginger, and more salt and pepper as needed. Pour this mixture over contents of casserole, and bake uncovered about one hour in an oven at 250 degrees F (120 degrees C).