Preheat the oven to 180 C / 350 F.
Place the chicken on the chopped onion and carrots in a deep-sided roasting pan.
Mix all the liquid, mustard, and herbs together and pour this sauce over the chickens and into the cavity.
Drizzle over the olive oil and season the birds with salt and pepper and roast uncovered for 1 1/2 hours and until the chickens are cooked.
I roast with the breast side up for 30 minutes, then flip them so the underside goes golden for the next 30 minutes and then flip it back upright for the final 30 minutes.
Strain the pan juices, onion, and carrot, and use this delicious jus as your gravy.
I like to cut the chicken up into rustic big pieces and then pour it over the pan sauce so they wallow in it before serving.