Place chicken in a roasting tin, drizzle with oil and season. Roast for 30 minutes, until cooked through. Allow to rest for 30 minutes. Remove meat from the bone and cover until needed.
Beat the blue cheese in a bowl add, sour cream, mayonnaise, white wine vinegar and salt and pepper. Mix well.
Spread each slice of bread with some blue cheese dressing, top with lettuce, tomato, cucumber finishing off sliced chicken and garnish with spring onion.
Serve remaining dressing on the side.