Place the chicken breasts in a saucepan and cover with cold water. Bring to a simmer and cook until cooked through, about 10 minutes. Drain and let cool.
In a salad bowl, combine spring onions, apples, celery, basil and blue cheese. Chop the chicken and add it to the salad. Drizzle with oil and lemon juice and season with salt and pepper, then toss to combine.