While the pork is cooking, use your kitchen scissors to slice open the peppers. Remove the seeds, veins, and then slightly roast them for a few seconds on each side on a warm skillet, but do not allow them to burn.
Cover with hot water and leave to soak for about 20 minutes. Drain thoroughly.
Put ¾ cups of water into the blender, a few of the chilies, garlic, cumin, oregano, peppercorns, bay leaves, cloves, thyme, cinnamon and the little piece of avocado seed, and blend for at least 1 minute.
Add a ½ cup of the soaking water and blend for a few more seconds to mix thoroughly. Add the rest of the chilies a little at a time and blend until smooth, adding more water as needed to mix thoroughly. If you have one of those modern blenders with higher capacity and more power, then you can process the salsa in just one step, pouring 2 cups of the soaking water in the blender with the peppers and spices and blending until you have a very smooth sauce.
Pass the sauce through a strainer and add to the pot with the meat. Cook over medium heat for 10 more minutes and stir frequently to prevent sticking. Add more water as needed, salt to taste, and keep stirring until the sauce thickens to the consistency of thick gravy. This will take about 15 minutes.