This dish transcends the simplicity of squash and the hominess of coarse-ground cornmeal. The lushness of the flavors soothe and satisfy the palate, creating culinary magic on a brisk winter evening. The whole dish, virtually a meal on its own, can be made in about an hour and is best served hotwhen the polenta is still steaming, the Parmesan is melting and the colors are vibrant. If you wish to accompany the squash with other courses, consider an appetizer or soup with mild flavors, like a simple vegetable broth filled with lightly cooked greens or rounds of toasted wheat bread spread with a mild hummus dip. To complement the assertive squash flavors, offer sliced fresh fruit.