Heat the oil in a skillet over medium heat. Lightly season the chicken breast with salt and pepper then add to the pan. Cook for 10 minutes then flip and cook for a further 10 minutes. After 5 minutes, add the butter into the pan along with the bay leaves and tarragon, once the butter starts to foam spoon it back over the chicken. Remove from pan and set aside to cool.
Toast the walnuts in a dry pan over high heat for 11/2 minutes.
Slice the apples into large wedges then toss in 1 tablespoon lemon juice to prevent browning. Roughly chop the walnuts and slice the chicken breast.
In a small bowl, combine crème fraiche, honey, vinegar and remaining lemon juice and stir to combine.
To construct, layer ¾ of the water cress then top with half the apple and chicken. Repeat with remaining watercress apple and chicken drizzle with crème fraiche dressing and sprinkle over walnuts.