The corn. If you’re using the dried corn, place it in a non-aluminum pot, cover with about 3 quarts water and bring to a boil. Sprinkle in the mineral lime, stir well, continue to cook for several minutes more as the hulls on each corn kernel turn a deep orange. Turn off the heat and let stand for about an hour to cool and let the mineral lime do its thing. Pour the corn into a colander, set it under running water and rinse the kernels, rubbing them vigorously between your hands to remove all the orange-ish gelatinous-feeling hull. When you’re finished, the kernels should have been returned pretty much to their white or yellow state. You have now made what in Mexico is called nixtamal.
Scoop your nixtamalized corn (what you made or what you bought from a tortilleria or grocery store) into a soup pot, add 3 quarts of water and 1 tablespoon salt, set over high heat, bring to a boil, reduce the heat to medium-low, partially cover and simmer until the corn is tender, 3 to 4 hours. You’ll need to stir the corn from time to time and add a little more water to keep the level pretty much even—no kernels should be peaking up through the liquid. NOTE: This simmering can be done on low overnight in a slow-cooker or on high pressure in a pressure cooker in about 1 hour (reduce the liquid to 2 quarts). You have now made hominy or what in Mexico is called pozole.
If using canned hominy, set it aside without draining.
In a blender jar, combine tomatillos, green chile and onion. Measure in ½ cup of the chicken stock and blend until smooth.
In another soup pot, heat the olive oil over medium-high. When hot enough to make a drop of the puree sizzle sharply, add it and stir regularly until reduced to the consistency of tomato paste. While the tomatillo mixture is cooking, scoop the pumpkinseeds into the blender jar (no need to wash), add 1 ½ cups chicken broth and blend until as smooth as possible. Add the pumpkinseeds, herbs and remaining 2 cup chicken broth to the cooked-down tomatillos, stir and bring to a simmer. Simmer 30 minutes. (For the smoothest texture, re-blend the mixture, in batches if necessary, to a velvety texture.)
Finishing the pozole verde. Using a slotted spoon or mesh “spider,” scoop the hominy into the pumpkinseed base. Add enough of the corn cooking liquid to give the a brothy, soupy consistency. (If using canned hominy, pour it—liquid and all—into the pot. Add additional chicken broth to give the right consistency.) Scoop a little of the brothy sauce in with the sardines and mash until nearly smooth. Scrape back into the pot. Taste and season with salt, usually about 2 teaspoons.
Bring to a boil over medium-high heat, then stir in the chopped herb leaves. Add the mussels or clams to the pot, cover and bring back to the boil. Simmer until the bivalves open, gently stirring through the pot from time to time to ensure even cooking and determine when they are all open.
Divide the pozole verde between warm serving bowls. Top each with a showering of avocado, red onion, chicharrón and oregano. Pozole Verde is traditionally served with crispy tortillas (tostadas), but crusty bread is good too.