Melt the lard in the saucepan and sauté the onion. Add the potato cubes, season with pepper, pour in the vegetable stock. Stir in the beans and simmer for about 30 minutes, until everything is soft and creamy.
Then mix in the savory and stir in the apple cider vinegar, which approximates the taste of sour beans, but does not come close to the strength of the lactic fermented ones.