Puree the beans with the water in a food processor or blender to the consistency of a smooth, mashed-potatolike paste. (The beans can also be mashed with the water by hand) Add the tahini, lemon juice, garlic, salt and cumin. Continue mixing until light and fluffy. Put into a serving bowl and swirl in the olive oil. Sprinkle on paprika and garnish with lemon slices and chopped parsley. Serve at room temperature.
