Toast the English muffin and set aside.
In a bowl, add the chicken and some of the Caesar Dressing and toss to combine.
Layer both halves of the English muffin with lettuce, tomato and onion slices, if desired. Spoon the chicken salad mixture evenly on top.
Place the avocado, garlic, lemon juice, Worcestershire, mustard, Parmesan, salt, pepper, anchovy paste, if using, plus 6 tablespoons water in a food processor or powerful blender and mix until thoroughly combined and smooth.
Adapted from "From Junk Food to Joy Food: All the Foods You Love to Eat...Only Better" by Joy Bauer © Hay House Inc. 2016. Provided courtesy of Joy Bauer. All rights reserved.