For the chimichurri, wash and chop the herbs. Peel and chop the garlic. Put all ingredients in a tall bowl. Puree and season to taste.
For the Argentine sweet potatoes, place the beans in a sieve and drain. Peel and dice sweet potatoes and cook in salted water until they are firm to the bite. Peel the onion and garlic and dice both.
Heat the olive oil in a pan and sweat the onion with the garlic in it. After 4 minutes add the sweet potato cubes and continue frying. After another 3 minutes add the black beans and fry everything together for 5 minutes on a low heat.