Peel the pears. In a saucepan over medium-high heat, combine sugar, water and wine. Heat until sugar is dissolved. Reduce heat to low.
Place pears bottom side down in liquid.
Cover and simmer for 25 minutes or until pears are soft, but not mushy. In a separate bowl, combine sugar and egg yolks, mixing until canary yellow. Add flour and blend. Whisk in half of the hot milk, then add this mixture plus the remaining milk to the double boiler. Add vanilla and cook over low heat, whisking constantly, until the sauce thickens slightly.