- In a medium saucepan, poach boneless, skinless chicken breasts with a pinch of sea salt and enough water to cover chicken. Bring to a boil then reduce to a simmer and cook, covered, until chicken is no longer pink inside, about 10 minutes.Remove from heat, then drain water and shred chicken using a fork; set aside.
- In a food processor, combine finely chopped fresh basil, raw unsalted walnuts and garlic clove; pulse until finely chopped. With the motor running, slowly add 1/4 cup olive oil; pulse until well combined.
- Transfer pesto to a large mixing bowl; add shredded chicken, 1/4 cup finely chopped red onion, juice of lemon, fresh lemon zest, salt and fresh ground black
- pepper, to taste. Add balsamic vinegar. Mix well to combine.
- Toast whole-grain bread. Arrange 4 bread slices on a work surface. Top each slice with chicken salad mixture. Divide romaine lettuce, chopped, optional, over top. Sandwich with remaining 4 slices of bread.