Finely dice the bacon for the filling. Wash 4 stems of thyme and shake dry. Peel and finely dice the shallots. Mix bacon and shallots. Wash the duck, dab dry and rub with salt and pepper from the inside.
Fill the duck with the filling, bay leaf and thyme, stick together with wooden skewers and tie up with kitchen twine. Melt 75 g butter in a large roasting pan, dust with flour and allow to brown a little.
Brown the duck thoroughly on all sides. Finally, the duck should lie with its back on the bottom of the pot. Season the breast with salt and pepper. Deglaze with stock. Bring to the boil and cook over medium heat for about 1 1/2 hours.
Sprinkle the duck breast several times with a total of 7-8 tablespoons of cognac. Meanwhile peel the onions and cut them into slices. Wash, peel and slice the turnips. Then remove from the roaster, place on a fat pan and bake in a preheated oven (electric range: 225 °C/ convection oven: 200 °C/ gas: level 4) for 15-20 minutes.
Melt 25 g butter in a saucepan. Add turnips and onions and fry while turning. Sprinkle with sugar. Let it caramelize for 5 minutes while turning. Add 3 tablespoons of cooking fat to the duck, add 5 tablespoons of cognac and cook over a low heat for 8-10 minutes.
Season again with salt, pepper and sugar. Wash 4 stems of thyme, shake dry, pluck leaves generously from the stems and add to the vegetables. Keep vegetables warm. Remove the duck from the oven, cut it into pieces and arrange on a plate with the vegetables and stuffing.
Garnish with thyme.