Ask the butcher to cut the calf's foot into four pieces. Cut the tripe into small squares and put them into a large pan. Cover with the water and bring to a boil. Lower the temperature and simmer, uncovered for about 2 hours, or until the tripe and foot are just tender but not too soft. Meanwhile, toast the chilies. Then slit them open and remove seeds and the veins from the chili poblano, cut into strips. Add to the meat while it is cooking. Remove the pieces of calf's foot, cool to handle, then strip off the fleshy parts. Chop roughly and return them to the pan.

Pour in the hominy, cooking the menudo slowly, uncovered, for an additional 2 hours. Add salt to taste. Sprinkle with oregano and serve in large, deep bowls.