For the salad: Cook the bacon in a large skillet over medium heat until crisp, about 10 minutes. Transfer to paper towels to drain.
Arrange the watercress, blue cheese, eggs, avocados, tomatoes, lettuce and bacon in rows on a platter. Season with salt and pepper.
For the dressing: In a small bowl, using a fork, mix the egg yolks into the mustard to make a paste. Whisk in the maple syrup, vinegar and Worcestershire sauce. While whisking, slowly drizzle in the oil to form a thick dressing. Add 1 tablespoon (15 ml) water to loosen it up if necessary. Whisk in the chives. Season with salt and pepper.
To serve, drizzle the dressing over the salad.