In a skillet over medium heat combine pecans and 3 tablespoons sugar. Cook and stir until the sugar melts and caramelizes about 3-4 minutes. Carefully transfer coated pecans to a sheet of wax paper or foil. Let cool; break into pieces.
Meanwhile, for the dressing, in a small bowl whisk together vinegar, mustard, garlic and remaining 1 tablespoon sugar. Slowly whisk in oil. Season with salt and pepper to taste.
In a large serving bowl layer lettuce, pears, blue cheese, avocado and green onions. Add dressing; toss to coat. Sprinkle with cooled pecans and serve.