Toss the pears with the sugar, salt, and pepper in a medium bowl until the quarters are evenly coated.

Heat the oil in a 12-inch nonstick skillet over medium-high heat until the oil shimmers. Add the pears in a single layer and cook without moving them until they are deeply browned on one side, about 3 to 5 minutes.

Turn the pears over and pour the balsamic vinegar into the skillet. Continue to cook, stirring gently to coat the fruit, until the vinegar has reduced to a thick, syrupy glaze and the pears are tender, about 2 minutes. Transfer the pears to a plate to cool slightly while you assemble the salad.

Whisk the balsamic vinegar and minced shallot together in a large bowl. Slowly stream in the olive oil while whisking constantly until the dressing is emulsified, then season with salt and pepper to taste.

Add the torn lettuce and watercress to the bowl with the vinaigrette and toss gently until the leaves are evenly coated.

Divide the dressed greens among individual plates or a large platter. Top with the warm glazed pears, toasted pecans, and shaved Parmesan, and serve immediately.