Clean the beans, unthread if necessary, cut into thin oblique slices (preferably with a bean slicer), cook with bundled savory (remove again after 10 minutes) in lightly salted water, but not too soft. Drain on a colander, save the broth.
Brown the bacon in the frying fat, fry the onions in the bacon fat until translucent, then add the flour and let it turn light yellow while stirring. Deglaze with meat stock and 1/4 l of boiled beans and cook for 8 minutes while stirring. Season to taste with salt, pepper, vinegar and sugar.
Add the beans and let them get hot, sprinkle with the chopped parsley. Serve with boiled potatoes, bratwurst or meatballs.