• Preheat oven to 200C. Chop potatoes into halves or quarters and parboil in a large saucepan of boiling salted water until they soften (approx 10-15mins). Cut onion into wedges and place in a roasting pan, sitting chicken on top of onion wedges. Roughly tear or chop rosemary leaves then rub with oil, salt and pepper all over chicken.
• Drain potatoes and shake in pan to roughen up. Roast chicken for 1 hour and 20 mins, or until golden and cooked through (strongly recommend purchasing a meat thermometer to be sure). Place potatoes in a separate roasting tray with oil, a pinch of salt and pepper, crushed garlic and the remaining rosemary leaves. Toss well to combine and roast in oven for an hour, or until golden.
• Remove chicken from oven, transfer to a platter and cover, leaving the remaining veg in the oven. Blanch peas in boiling water for 2 mins. At this point you can use the tray with cooking juices to make gravy (add 1 tbsp of flour on the stove top, stir in 600ml of boiling water and stir until you reach desired consistency). Serve everything in the middle of the table.
Swap peas for any preferred or available green veg.