In a small bowl, whisk together the minced garlic, Dijon mustard, mayonnaise, and red wine vinegar until well combined. Slowly drizzle in the olive oil while whisking constantly to emulsify the dressing and create a creamy, cohesive sauce. Season with sugar, salt, and pepper to taste. I like to taste the dressing and adjust the vinegar or salt as needed—a well-balanced vinaigrette makes all the difference in a cobb salad.
While the dressing rests, prepare all the salad ingredients for assembly. Chop the lettuce into 1-inch pieces and place in a large salad bowl. Dice the tomatoes into 1/2-inch pieces and cut the cooked chicken into 1/2-inch cubes. Quarter the hard-boiled eggs and finely dice the onion. Have the crumbled bacon, crumbled blue cheese, and fresh chives ready. For the avocado, cut it in half lengthwise, remove the pit, and dice the flesh into 1/2-inch pieces just before adding to the salad—this prevents browning.
Add all the prepared ingredients from Step 2 to the bowl with the lettuce, arranging them in rows or mixing them together depending on your preference. Pour the vinaigrette from Step 1 over the salad and toss gently but thoroughly to coat all components with the dressing. I recommend tossing the salad just before serving to keep the lettuce crisp and the avocado from getting crushed.