In the bowl of the slow cooker, combine the sugar, ginger, and butter. Add the pears and gently toss to coat. Arrange the pears cut-side down. Set the slow cooker to high and cook, covered, until the pears are tender and easily pierced with the tip of a knife, about 1 to 2 hours. Divide the pears and ice cream among individual bowls and drizzle with the sauce.
If You Don't Have a Slow Cooker: Heat oven to 325° F. Follow the recipe above using a Dutch oven or casserole. Bake, covered, turning once, until the pears are tender and easily pierced with the tip of a knife, 1 to 2 hours.