Peel the turnip, cut it into long pieces and then into thin slices. Peel and wash the potatoes and cut them into thin slices. Bring the stock to the boil, cook the turnips and potatoes for about 1 minute. Take out and put in 4 ramekins alternately. Add cream to the stock, bring to the boil and add sauce thickener. Season with salt and pepper.
Wash pork fillets, dab dry and cut into 12 medallions. Season with salt and pepper. Heat oil in a pan and fry the medallions in it for about 1 minute on both sides. Place 3 medallions on each gratin. Pour the sauce over the potatoes, turnips and meat and bake in a preheated oven (electric cooker: 200 °C/ gas: level 3)
Bake for about 15 minutes. Garnish with parsley