in a large nonstick skillet, heat butter oven medium heat. Add carrots, parsnips, sugar and salt and pepper to taste; cook until the vegetables are lightly browned, about 3 minutes. Add half c of the stock, cover the pan and simmer until tender, about 10 minutes. Transfer to a dish and set aside. Add leeks and the remaining quarter c stock to the skillet, season with salt and pepper, cover the pan and simmer until tender, about 10 minutes. Add the reserved squash, carrots and parsnips and toss gently. Taste and adjust seasonings, adding a grating of nutmeg. Simmer for an additional 3 to 4 minutes to warm through before serving.