1) Place an oven rack in the lower third of the oven. Preheat the oven to 230°C/gas mark 8.
2) Rinse the poussins and pat dry with paper towels. In a small bowl, mix together the olive oil, shallots, orange zest, lemon zest, thyme, mint, salt and pepper. Rub two tablespoons of the zest mixture over the skin of the poussins. Place the remainder of the zest mixture under the skin and into the cavities of the hens. Using kitchen string, truss the legs together. Place the poussins in a shallow 23cm x 33cm baking dish.
3) Add the chicken stock, Marsala wine, lemon juice, orange juice and cranberries. Roast for 30 to 35 minutes, or until the leg juices run clear. Remove the poussins and set aside.
4) Place the flour in a small saucepan. Whisk in the pan juices and bring to a boil over a medium heat. Reduce the heat and simmer for 8 to 10 minutes until slightly thickened. Whisk in the butter and season, to taste, with salt and pepper.
To serve, remove the kitchen string and place the poussins on two serving plates. Drizzle with the citrus-herb sauce.
Cook's note: Reserve four tablespoons of the citrus-herb sauce for the crouton salad recipe.