Stuffed Roast Pork with Plums and Onions

Preheat the oven to 200°C (approximately 400°F).

Rinse the oranges in hot water, finely grate the peel of 1 orange, squeeze both oranges, and mix juice and zest with the mustard seeds.

Peel potatoes and the celery root, dice and cook in boiling salted water until tender, 10-15 minutes. Then drain and mash. Rinse the thyme sprigs, pluck off the leaves and mix with the mashed potatoes and celery root, stir in the cornstarch and mix with the egg. Season with salt and pepper.

Peel the onions and cut them lengthwise into thin strips. Rinse the plums, cut in half, remove the pits and cut into wedges.

Rinse the roast, pat dry and season with salt and pepper. Spread the potato mixture on top, roll tightly, cover with slices of bacon and tie with kitchen twine. Rub the roast with the orange juice mixture and mustard seeds and place with the butter in a roasting pan. Pour over the remaining orange juice and place in the preheated oven. Roast for 10 minutes, then add the white wine and some chicken stock and roast for about 1 hour and 15 minutes. Baste occasionally with the stock.

Take the roast out of the roasting pan and place on a plate. Toss the plums and onions with meat juices in the pan. Roast in oven until crispy, about 30 minutes.