THE NIGHT BEFORE
1 Remove the papery bitter skins from the walnut pieces. (This is the hard part.) Sometimes the skins easily rub off. I have found that usually, for us, the skins don't easily peel off and we need to blanch them for one minute in boiling water first, to loosen the skins. If you blanch the walnuts, let them cool to the touch and carefully peel off as much of the bitter skins as you can. This is painstaking work, but unless your walnuts are shed of their bitter skins, the sauce may be a bit bitter.
2 Place the walnuts in a bowl, cover them with milk to soak, and chill them overnight in the refrigerator.
THE DAY OF
Roast the chiles:
3 Place the chiles directly over the flame of a gas stove, or place under a hot broiler, to char the outside tough skin. Turn the chiles to char them on all sides. Get as much of the outside skin blackened as possible, it will be easier to remove that way. (See How to roast chile peppers over a gas flame tutorial using Anaheim chiles.)
4 Place the blackened chiles in a bowl and cover with a plate or damp clean towel and let sit for 20 minutes. The burned skin will then flake off very easily and the flesh will become a little more cooked in the steam. Make a slit in the side of each chili and carefully remove the seeds and veins. Be careful to leave the top of the chili, the part around the base of the stem, intact. (A tip from Diana Kennedy: if you taste the chiles and they are too spicy hot, soak them in a mild vinegar and water solution for about 30 minutes.) Rinse the chilies and pat them dry.
Make the walnut sauce:
5 Drain the walnuts. Place the soaked and drained walnuts, the queso fresco, sour cream, sugar, and cinnamon into a blender and purée until completely smooth.
Make the picadillo stuffing:
6 Heat one tablespoon of the oil in a large wide saucepan on medium high heat. Working in batches to prevent crowding the pan, brown the meat on at least one side, sprinkling the meat with a little kosher salt as it cooks. Add another tablespoon of oil if needed for the subsequent batches. Remove meat to a bowl and set aside.
7 Add a tablespoon of cooking oil to the pan and heat on medium heat. Add the onion and cook until soft. Add the cinnamon, black pepper, cloves, and garlic and cook another minute.
8 Melt butter in the pan and return the ground meat to the pan and use a wooden spoon to break up any clumps. Add the crushed tomatoes, golden raisins, and chopped slivered almonds. If the mixture seems a little dry, add a tablespoon or two of water. Add chopped apple to the picadillo mixture. Adjust spices, add more cinnamon, salt, ground cloves to taste (go easy on the cloves, they can overpower).
Assemble the chiles en nogada:
10 Stuff the chilies with the picadillo until they are well filled out. Place them on individual plates or on a serving platter.
11 To serve, cover the stuffed chiles with the walnut sauce and sprinkle with pomegranate arils and chopped fresh parsley or cilantro.