Wash collard leaves and pat dry with paper towel. Cut the stem out lengthwise from the collard leaf; set aside. Heat olive oil and cook chicken breasts in a skillet over medium until thoroughly cooked. Let cool and shred into small pieces. Transfer chicken to a medium-sized bowl. Stir mayonnaise, relish, dried cranberries, salt and pepper with chicken. Spread chicken salad onto each collard leaf section. Roll up from bottom to top. Place seam side down in refrigerator for 1-2 hours.