Combine first 5 ingredients in a pot. Place over medium-high heat and bring to a boil, stirring to dissolve the sugar. While this occurs, peel and core the pears. (A melon baller works well to core the pear from its blossom end). Trim a little from the bottom so the pears will stand up. Add pears to the syrup, cover pan, and reduce heat to medium-low and gently simmer, turning them from time to time, until pears are just tender, about 15-20 minutes. Remove from heat and allow pears to cool in syrup, turning them over from time to time.
Using a slotted spoon, transfer pears to a plate, standing them up. Store pears in the fridge until needed. To make the sauce, boil 1 1/2 cups of the poaching liquid until reduced by 2/3, and then remove and chill. To serve, spoon a little sauce on a dessert plate. Place pear in the centre and set or pipe a large spoonful of mascarpone cheese or whipped cream alongside. Garnish with mint and serve.