There are two unusual avocado ingredients in this recipe, leaves and a bit of the pit: You can skip both or just one, if you want, but they add flavor.
Cut the pork into chunks between 1 and 2 inches across. Just barely cover with water and bring this to a simmer. Skim any froth. Add salt to taste and the avocado leaves and simmer uncovered until the water has almost cooked away.
Meanwhile, pour boiling water over the guajillo, ancho and arbol chiles and let them steep to rehydrate.
When they're soft, add the chiles, the garlic, cumin, thyme, cloves and avocado pit to a blender. Add some water or stock and puree. You want this to be about as thick as melted ice cream or housepaint.
When the water is almost all gone, remove the avocado leaves and add the lard. Turn the heat to medium-high and brown the pork, stirring often.
Once the pork has browned, pour in a little water or stock and use a wooden spoon to remove any browned bits off the bottom of the pot. Now pour in the contents of the blender and stir. Add a little water to the blender to get any good stuff out of it and add that to the pot, too. Return the avocado leaves to the pot, add the orange juice and zest and salt everything to taste. Let this simmer until the sauce thickens a bit, about 15 to 20 minutes.
Serve alongside rice and beans, or in a corn tortilla.
Notes
Variations
Some cooks add a bottle of Mexican coke to the mix; this is most common in Coahuila.
You can skip the orange juice and use 1/4 cup of cider vinegar.
Sometimes you will see a little Mexican chocolate added. If you want to do this, grate 1/2 a Mexican chocolate tablet and add it to the blender.