For Sauce: Melt butter in heavy large skillet over medium-high heat. Add onions; sauté 5 minutes. Add walnuts. Sauté until nuts are slightly darkened, about 12 minutes. Mix in the remaining ingredients. Reduce heat to medium. Simmer until sauce thickens, about 15 minutes. Season with salt and pepper. (Can be made one day ahead. Cover; chill. Rewarm, thinning with more broth if desired.).
For Chicken: Prepare barbecue (medium heat). Mix molasses and cinnamon. Brush chicken with olive oil and sprinkle with salt and pepper. Cook chicken glazing in the last minutes of cooking.