Dab meat dry and season with pepper. Wrap bacon around the meat and prick several times with a fork. Peel onions and 2 cloves of garlic, dice very finely. Mix with brown sugar, 2 tablespoons vinegar and soy sauce.
Pour the marinade over the fillets and turn them over. Cover and chill overnight. The next day peel, wash and dice the potatoes. Mix in a bowl with paprika, salt, pepper and 100 ml oil.
Spread on a baking tray. Roast in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for 40-45 minutes until golden brown. Take out and let cool down.
Place the fillets with the marinade on the fat pan of the oven. Cook in the preheated oven (electric cooker: 125 °C/ circulating air: 100 °C/ gas: see manufacturer) for approx. 1 1/2 hours. Clean, wash and cut the peppers into small cubes.
Peel 3 garlic cloves and throw them finely. Clean the chillies, cut lengthwise, wash and remove the seeds. Chop the pods finely. Wash and clean spring onions and cut into fine rings. Wash herbs, shake dry.
Pluck or strip off leaves and chop finely. Set aside some parsley for garnishing.
Mix potatoes with paprika, chili, spring onions and herbs. Whisk 6 tablespoons vinegar with salt, sugar and pepper, stir in 150 ml oil. Mix into the salad, set aside. Take the fillets out of the oven and let them drip off on kitchen paper.
Pour sauce through a sieve into a pot and bring to the boil. Stir starch with a little water until smooth. Thicken sauce with it, season to taste. Heat 2 tablespoons of oil in a large pan, fry the fillets all around.
Season yoghurt with pepper. Season the salad again. Add yoghurt. Arrange fillets, drizzle with some sauce and sprinkle with parsley. Add potato salad and remaining sauce.