Poach the Chicken: Place the chicken breasts in a wide pot or pan and cover by about an inch with cold water. Season the water with salt. Turn the heat to medium until it reaches a gentle simmer. Then reduce the heat back to low and cover the pan. Let the chicken simmer for 8 to 12 minutes, or until the internal temperature reaches 160°F to 165°F. Remove the chicken and let it rest for a couple of minutes. Then chill in the fridge.
Prepare the Chicken: Transfer the cooled chicken to a cutting board and dice it into ½-inch pieces. Add it to a large mixing bowl. This uniform size ensures each bite has the perfect amount of chicken and makes for easier mixing with other ingredients.
Combine Ingredients: Slice and dice the celery, green onion, grapes, parsley and tarragon. Add those ingredients to the mixing bowl along with the almonds, mayonnaise, Dijon mustard, and lemon juice. Season with salt and pepper. The combination of fresh herbs, crunchy vegetables, and sweet grapes creates a balanced flavor profile.
Mix and Chill: Mix everything together until it's well combined. Let it chill in the fridge until you're ready to serve. This resting time allows the flavors to meld together, resulting in a more cohesive and delicious chicken salad.