How to Make It
Using a large citrus reamer, squeeze 1/2 cup of juice from the pomegranate halves. Transfer to a small saucepan and boil until it is reduced to 3 tablespoons, about 10 minutes. Transfer the pomegranate syrup to a small bowl and whisk in the vinegar and then the oil. Season the dressing with salt and pepper.
In a medium saucepan, combine the water and sugar and bring to a boil, stirring until the sugar dissolves. Add the quinces and set a small lid or heatproof saucer directly on top to keep the wedges submerged. Cook over moderate heat until just tender, about 10 minutes. Using a slotted spoon, transfer the quinces to a plate to cool. Cut the quinces into thin wedges.
In a large skillet, cook the pancetta over moderate heat until crisp. Drain the pancetta; reserve 1 tablespoon of the fat in the skillet. Return the skillet to high heat, add the endives and cook, tossing, until just warmed through. Add the quinces, pears and pancetta, season with salt and pepper and toss gently. Transfer the salad to a platter. Drizzle with some of the dressing, sprinkle with the tarragon and serve. Pass the remaining dressing separately.