Preheat the oven according to the instructions on the packet. Put a baking tray in the oven to heat up for 5 minutes. Tip the frozen potatoes onto the tray and roast for 30-40 minutes until golden or according to the timings on the packet.
Mix the mushrooms, tomatoes, parsley and cheese together in a bowl and season well. Put the chicken breasts on a board and slice about two-thirds through the middle horizontally. Open each out and spoon half of the mushroom mixture onto each. Flip the chicken over onto the top and drizzle over the oil and season well. Transfer to the tray and roast for 20-25 minutes.
Bring a small pan of cold salted water to the boil and add the green beans. Cover and cook for 3-4 minutes until tender. Drain well, return to the pan and add the butter. Season well.
Crush the potatoes lightly, then divide between the two plates, along with the green beans then place a stuffed chicken breast onto each, too, and serve.
