For the pork belly with yogurt sauce, first prepare the sauce. To do this, peel the onion and then chop it finely. Heat about 30 g of butter in a saucepan, sauté the onion in it, sprinkle the flour over it and add the yogurt, stirring constantly.
Add the double sauce and the green peppercorns. Season with the spices and simmer for about 10 minutes at low temperature with the lid closed.
Heat the remaining butter in a frying pan and brown the meat slices in it on both sides. Remove and keep warm. Add the roast stock to the sauce and heat briefly again.
Arrange the pork belly with yogurt sauce and serve.