Peppercorns give a spicy edge to this unusual and delicious frozen yogurt.
Place yogurt in a fine strainer set over a bowl. Refrigerate for about 1 hour, until about 1 cup liquid had drained from the yogurt. Discard liquid; set yogurt aside.
Meanwhile, peel core, and chop pears into 1/2-inch pieces. Combine pears, sugar, lemon juice, vanilla bean, peppercorns, and bay leaf in a medium saucepan and simmer over medium-low heat until the syrup thickens and pears are very soft, about 25 minutes. Remove and discard the vanilla bean and bay leaf.
Set a medium bowl in an ice-water bath. Transfer pear mixture to a food processor and puree until smooth, about 2 minutes. Pass puree through a fine strainer into the bowl over the ice bath, discarding solids. Let stand until chilled.
Remove from ice-water bath; whisk yogurt into pear mixture. Transfer to an ice cream maker and freeze according to manufacturer's instructions. If necessary, do this in 2 batches, keeping remainder refrigerated while freezing first batch.