Preheat the oven to 200°C. Chop up the onion, the garlic cloves and the stick of celery. Set aside 10 leaves of celery. Melt the butter in an ovenproof casserole dish, dust the pieces of meat with flour and brown them in the butter, turning them over frequently. Remove the meat, wipe the casserole dish, add the olive oil and sauté the aromatic herbs, add the veal pieces, season with salt and pepper and then add the Pommeau and leave to reduce.
Pour over the hot chicken stock, cover and cook in the oven for 90 minutes.
Peel the celeriac and cut into 2cm cubes. After an hour in the oven, turn down the temperature to 160°C and add the celeriac, cover the casserole dish and continue cooking in the oven. Cut three unpeeled apples into cubes of the same size and add them to the casserole dish and continue cooking, covered, for the last 15 minutes. Chop up 10 celery leaves, peel and cut the last apple into small cubes and mix this with the celery adding a squeeze of lemon juice.
Set aside. Serve topped with raw chopped apple/celery garnish.