Combine all the ingredients for the marinade in a shallow dish. Add the chicken breasts and leave to marinate at room temperature for 2 hours, or in the refrigerator for 24 hours.
Heat a griddle pan (or ordinary frying pan). Place the marinated chicken breasts in the pan to cook for 8–10 minutes on each side. When cooked, remove the chicken from the pan and slice it into long strips.
Place the tortillas under a preheated grill and cook for 30 seconds on each side. Spread over one side of each tortilla a spoonful of soured cream, a little tomato, avocado and a sprinkling of spring onions and red onion.
Add the pieces of griddled chicken and season. Roll up each tortilla tightly and cut in half across each one. Serve with tortilla chips, if liked.