Place the chicken in a roasting pan and dot with pieces of butter. Season with the salt, pepper and herbs. Peel the cloves of garlic and crush. Peel the shallots and cut them in half. Arrange the crushed garlic cloves, shallots and potatoes around the chicken. Drizzle with olive oil and roast for 1½ hours. Halfway through, turn the chicken over and stir the potatoes.