Bring the water to a boil in a pot. While the water begins to boil, cut the green beans into small pieces. When the water is boiling, add the green beans to the water. Then, grind the mace, dried serrano chili, cumin, onion, and garlic in a blender. When the green beans are slightly cooked, add the ground salsa and continue boiling the salsa and green beans until the green beans are cooked. Lower the pot and it's ready to eat.