1 cup walnut
2 cups cilantro
1 jalapeno pepper
1 tsp salt
2 tbsp cider vinegar

Put the walnuts in a food processor and grind until fine. Add the cilantro, jalapeño pepper, salt, vinegar and 2 to 3 tbsp of water and blend. Blend in a little more water if necessary to make a thick sauce. Taste and correct the seasoning, adding more salt if necessary.