1. Preheat oven to 425°. Peel, halve, and core pears and put cut side up in an 8- or 9-in. square baking dish. Pour sherry on top. Scrape seeds from vanilla bean with side of a knife and add to sherry with pod. Drizzle pears with honey and dot with butter.
2. Roast, basting twice with juices, until pears are just tender when pierced, about 10 minutes.
3. Transfer ingredients to a deep bowl and let cool at least 2 hours, turning pears occasionally, or chill overnight. Strain before using, discarding vanilla pod; save syrup to use in cake batter and to serve with pancakes if you like.
*Find Oloroso sherry, a full-flavored, somewhat sweet sherry, in the wine section.