1/2 cup thinly sliced green onions (white and pale green parts only)
2 teaspoons plus 2 tablespoons fresh lemon juice
2 large skinless boneless chicken breast halves
3 tablespoons extra-virgin olive oil
4 lemon wedges
Directions
Blanch watercress in pot of boiling salted water 30 seconds; drain. Cool. Squeeze out excess water. Finely chop watercress. Mix watercress, mayonnaise, onions, and 2 teaspoons lemon juice in small bowl to blend. Season with salt and pepper. (Can be made 2 days ahead. Cover and chill.)
Place each chicken breast between sheets of plastic wrap. Using meat mallet or rolling pin, pound chicken to 1/2-inch thickness. Cut each chicken breast lengthwise in half. Place chicken in glass baking dish. Pour remaining 2 tablespoons lemon juice and olive oil over chicken. Sprinkle with salt and pepper. Turn to coat. Cover and refrigerate at least 1 hour or overnight.
Heat heavy large skillet over medium-high heat. Remove chicken from marinade. Working in batches, sauté chicken until cooked through, about 2 minutes per side. Transfer to 4 plates. Garnish each with dollop of mayonnaise and lemon wedge.