Place the ribs in a large pot and add water until it barely covers the ribs. Add the onion wedge, garlic cloves, bay leaves and salt. Bring to a simmer and keep simmering for 1 hour over medium-low heat. Skim off the scum foam with a slotted spoon or skimmer. After 1 hour the ribs will still be firm. Pass 1 1/2 cups of the broth in which the ribs boiled through a strainer and reserve. Discard the rest of the broth with all the solids.
Heat the olive oil in a large skillet over medium-high heat and quickly brown the ribs for about 1 minute on each side of each rib, until brown. You can skip this step if you choose too, although the browning adds an extra layer of flavor, for sure.
Make the Salsa Verde: In another pot boil the green tomatoes, onion, garlic and Serrano chili in some water for about 10 - 12 minutes, until the tomatoes change color. Turn off the heat and let them cool down. Place the boiled ingredients in the blender, add some of the cooking water to the blender along with the bunch of cilantro and the cube(s) of chicken bouillon and some freshly ground pepper (you can use table salt instead of the cubes) and the ground cumin. Process until smooth and transfer to a large pot. Add the ribs into the Salsa Verde pot along with the browning oil. Add the jarred Nopalitos (if using) and the cubed potatoes. Add the 1 1/2 cups of the reserved pork broth and simmer over medium-low heat for 30 - 40 minutes until the potatoes are cooked through.
Enjoy with rice and/or beans and warm corn tortillas!
