Peel pears, leaving stems intact, and cut a thin slice from bottom of each if necessary to enable pears to stand upright when served. Set aside.
Put sugar in a 3-quart heavy saucepan and melt over moderate heat until it begins to caramelize. Continue to cook, keeping a close eye and the sugar constantly circulating. Cook until the sugar is a deep golden caramel. Stir in the butter carefully, as the mixture may bubble up. Simmer and stir until caramel sauce has developed, about 5 minutes. Pour in wine and scrape in the seeds from the vanilla bean.
Carefully arrange pears in the poaching liquid. They should be completely covered by the liquid, add water if they are not. Simmer pears, turning them occasionally, until tender, about 20 minutes.
Test by inserting a knife into the fattest part of the pear, it should come out with no resistance. Finish off with lemon juice to wake up the flavor. Gently remove the pears to a serving dish, cut side down. Pour the wine syrup over the pears. Serve with gorgonzola and candied walnuts.
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