1. Preheat the oven to 190°C.
2. Make the stuffing by melting the first portion of butter in a small frying pan over medium heat. Add onion and sage and fry for 5 minutes stirring often, until the onion has softened. Add walnuts and stir through. Add to a bowl with remaining stuffing ingredients. Mix well and set aside. 
3. Fill the chicken cavity with stuffing, then tie the legs together with twine. Place chicken in a large roasting dish then season the chicken with salt and pepper and drizzle with oil.
4. Roast in the oven for 40 minutes. Using oven mitts remove the dish, add  second portion of butter to the dish and sage leaves. Scatter potatoes and garlic cloves around. Sprinkle generously with salt. 
5. Return chicken and potatoes to the oven for a further 50 minutes, or until the chicken is cooked through and the potatoes tender and golden. Rest the chicken for 10 minutes.
6. Serve with a green salad.

Note: if you don’t have baby potatoes simply halve or quarter full sized potatoes.