I've never seen this done in the States - have you? Does anyone know why keeping the stem sealed prevents ripening? Pears are one of the trickiest fruits to ripen; they start out unpleasantly hard and astringent, and it seems like they are at their peak for one elusive moment before they descend into mush.
We did discover one guide to ripening and caring for pears from a website that shows this practice:
• The Simple Pleasures of Conserving Fruits for Winter
We poached pears like these in red wine while in France; check out a similar recipe below.