Spread hazelnuts in a shallow baking pan and toast in 350 oven until pale golden about 10 minutes. Let cool slightly, then rub off as much of skins as possible with your fingers. Chop nuts coarsely and set aside.
In small bowl, stir together vinegar, honey and ginger, set aside. Halve and core the pears, brush cut sides with lemon juice. Line plates with lettuce leaves, arrange pear halves, cut side up on lettuce. Spoon on dressing and sprinkle hazelnuts.