Bake hazelnuts in a shallow pan at 350º, stirring occasionally, 5 to 10 minutes or until toasted. Cool, and chop.
Cook vinegar over low heat in a heavy saucepan, stirring occasionally, until reduced to 6 tablespoons (about 1 hour). Set aside.
Melt butter in a large skillet over medium-high heat; add chanterelles, and sauté until golden brown. Stir in shallots, garlic, thyme, and hazelnuts; sauté 30 seconds.
Spoon evenly on individual serving plates. Drizzle with balsamic syrup, and sprinkle with salt and pepper. Serve immediately.