1. Whisk vinegar, shallot, mustard, salt and pepper in a small bowl to combine.
2. Whisk in oil until combined.
3. Place salad greens in a large bowl.
4. Add half of the dressing and toss to coat.
5. Divide salad greens among 4 plates.
6. Arrange equal portions of chicken, egg, bacon, tomatoes, cucumber, avocado and blue cheese (if using) on top of the lettuce.
7. Drizzle the salads with the remaining dressing.
8. TIP:
9. *Tips To poach chicken breast: Place boneless, skinless chicken breasts in a medium skillet or saucepan and add lightly salted water to cover; bring to a boil. Cover, reduce heat to low and simmer gently until chicken is cooked through and no longer pink in the middle, 10 to 12 minutes.
10. **To hard-boil eggs: Place eggs in a single layer in a saucepan; cover with water. Bring to a simmer over medium-high heat. Reduce heat to low and cook at the barest simmer for 10 minutes. Remove from heat, pour out hot water and run a constant stream of cold water over the eggs until completely cooled.
11. Serves 4.