In a large, lined slow cooker, stir together the wine, sugar, cinnamon, cloves and star anise, if using. Add the pear halves and arrange, round side up, in an even layer. Add water, if needed, so that the pears are submerged. Cover and cook on high heat until the pears are fork-tender, about 2 1/2 hours.
Using a slotted spoon, transfer the pears to bowls. Top with ice cream and drizzle with a little of the cooking liquid.