Add all the marinade ingredients to a mixing bowl and whisk together to combine.
Use the back of a spoon to gently loosen the skin.
Use the spoon to insert marinade underneath the chicken skin.
Massage the chicken and spread the marinade evenly. Remember to add butter in the cavity as well.
Rub the remaining marinade all over the chicken.
Cover the chicken and rest for 2-3 hours or overnight.
Mix the sweet potato, onion, and garlic in a bowl.
Place some of the vegetables in the center of the roasting pan. Place breast-side up on top of the vegetables in the middle.
Place the remaining vegetables on the sides of the pan. Tuck the wings underneath the chicken
Rub the chicken with some olive oil and drizzle some over the vegetables as well.
Add half a cup of chicken stock to the pan.
Roast in the oven for 45-50 minutes.
Baste using the pan juices half way through cooking time.
Remove the vegetables from the roasting pan and move it to a serving platter.
Add 1 tablespoons of flour to the pan and whisk it with the pan juices.
Bring this mixture to a boil over low heat till the liquid thickens up to make a gravy.
To carve the chicken, first cut out the legs.
And it's ready. Serve hot along with the chicken and vegetables!