Heat oven to 220C/200C fan/gas 7. Tip the chicken pieces into a largish roasting tin and toss with the oil, onions and squash. Season with salt and pepper and arrange chicken so it’s all skin-side up.
Roast in oven for about 25 mins, remove, toss through sage, walnuts, then drizzle over vinegar. Using tongs, again arrange chicken so it’s all skin-side up. Roast for another 25-30 mins until chicken is golden brown and the veg soft and sticky. Serve straight from the tin with some mashed potato.