Preheat oven to 375 degrees F. Line a baking sheet with parchment. On the parchment, add the chicken breasts. Toss with the olive oil and sprinkle both sides of chicken with a few teaspoons of salt. Transfer to the oven and roast until the chicken is fully cooked and juicy, about 45 minutes, or until a thermometer into the center reads 165 degrees F. Set aside and allow to cool completely. When cool enough to handle, using two forks, shred the chicken.
Transfer to a medium bowl. Add the mayonnaise, black pepper, green onions, grapes, walnuts and a few pinches of salt. Give it a taste and adjust the flavor according to your liking. Spoon over your bread of choice and top with a few extra green onions.