03Discard all but 2 tablespoons of the fat from the skillet, add the onions, cut-side down, and saute until lightly browned. Add 3/4 cup of the stock, bring to a boil, and transfer the onions and stock to the casserole.
04Add the kohlrabi, carrots and garlic to the casserole. Bring slowly to a boil on top of the stove, cover tightly and place in the center of the preheated oven. Braise the chicken for 1 hour to 1 hour and 10 minutes, turning it once or twice and basting with the pan juices. The chicken is done when the juices run pale yellow. Transfer it to a baking dish, and set aside. With a slotted spoon remove the vegetables to a side dish, cover and reserve.
05Carefully deglaze the casserole, adding the remaining stock. Bring to a boil on top of the stove, and reduce by a third. Make a beurre manie by combining the remaining tablespoon of soft butter and the flour, mashing with a fork until thoroughly smooth. Whisk a bit of the beurre manie into the sauce until the sauce lightly coats a spoon. Taste, and correct the seasonings. Add the reserved vegetables to the sauce and keep warm.
06Remove and discard the trussing string, quarter the chicken, and place on a serving platter. Arrange the vegetables around the chicken, and spoon the sauce over the chicken. Garnish with sprigs of parsley, and serve immediately.