Place the meat in a large heavy pot. Add ¼ of the white onion, 2 bay leaves, and 2 of the garlic cloves. Cover with 1½ cups of water and turn the heat to high. Once it starts boiling, reduces the heat to low and gently simmers. Cooking the meat will take about 20-30 minutes, this will give you plenty of time to prepare the sauce and to precook the nopales.
While the meat is cooking, clean the peppers by removing the seeds and veins. Place them in a saucepan, cover with water, and turn the heat to medium-high. Once the water starts boiling, turn off the heat, cover the saucepan, and set aside for 20 minutes or until the peppers are soft.
Precooking the nopales: Place the chopped nopales in a saucepan, cover with 4 cups of water, and cook over a medium heat. As soon as the water starts boiling, reduce the heat and cook for 5 minutes. After this, remove the nopales from the heat, strain, and set aside.
By this time, the water in the pot where you’re cooking the meat should have been reduced, and the meat will start to brown in its own fat. Remove the garlic and onion. If the meat is too lean and doesn’t render any fat, add 2 tablespoons of lard or vegetable oil. Sprinkle with the 2 tablespoons of flour and stir well, browning the pieces of meat.
Drain the peppers from their soaking water. In a blender, place the peppers, ¼ of the white onion (chopped), 2 garlic cloves, cumin, and oregano, along with 1-½ cup of water. Blend on high until you have a very fine puree.
Pour the sauce over the cooking meat using a strainer (stir and add more water, if needed, to create a smooth sauce). Season the sauce with salt and pepper, and simmer for 15 more minutes until the meat is really tender and the sauce has thickened a little.
Stir in the cooked and drained nopales, and keep cooking for 5 more minutes. Taste to see if it needs some adjustment with the seasoning, I know some of you would like to add more cumin and oregano. Serve with rice, beans, and a stack of warm flour tortillas.