Preheat oven to 400°F.
Season the chicken with olive oil, salt and pepper, juice of half a lemon and fresh thyme.
Place the chicken in an ovenproof dish and roast for about 40 minutes or until internal temperature reaches 160°F.
Dice the celery and grapes and roughly chop up the nuts.
In a small bowl, combine mayo, Greek yogurt, mustard and caper brine. Mix well.
Once the chicken is cooked, remove from the oven and let it cool down.
Place the chicken into a large bowl and shred the meat into smaller chunks. Add the grapes, celery, nuts and the sauce. Mix well.
Carefully separate the lettuce head into single leaves.
Assemble the cups by placing about 2 generous tablespoons of the salad in each leaf. Enjoy!
