1) Preheat the grill.
2) Put the chicken between 2 sheets of waxed paper and pound with a mallet or hammer so the chicken is an even thickness of about 2-cm, then cut the chicken crosswise into 1-cm strips.
3) In a large bowl, combine the hot sauce and the oil, add chicken and toss until the chicken is well coated. Arrange the chicken on a baking sheet and grill until it is cooked through, about 4 to 6 minutes, turning once.
4) In a large bowl combine the cos, celery, shredded carrots and spring onions. Toss with the blue cheese dressing. Divide the greens between 4 plates, top with the chicken. Serve with extra hot sauce.
For the blue cheese dressing:
1) Fold a full sheet of paper towel into quarters and put it into a small bowl. Spoon the yogurt onto the paper towel and place in the refrigerator for 20 minutes to drain and thicken.
2) In a medium bowl, whisk the buttermilk and thickened yogurt into the mayonnaise until smooth. Add the vinegar and sugar and continue to whisk until all the ingredients are well combined. Stir in the blue cheese and season, to taste, with salt and pepper.