Preheat the oven to 350 degrees. Season the lamb all over with salt and pepper and place in a single layer in a roasting pan. Pour on the adobo sauce and toss to coat. Bake, uncovered, 45 minutes, then cover and bake 45 to 60 minutes longer, until the meat is soft and flaky.
Transfer the meat to a cutting board. Pour the pan juices into a bowl or measuring cup and skim and discard the fat. Shred the meat. The lamb and pan juices may be kept together in the refrigerator up to 5 days. Warm over moderate heat 5 to 7 minutes before assembling the tacos. When ready to make the tacos, preheat the oven to 350/.
Roast, peel, seed and slice the poblano chiles (see Note). Mix together the grated cheeses. Dip a corn tortilla in some water and shake off the excess. Toast one tortilla at a time in a nonstick pan over medium heat for about 1 minute on each side. Wrap in a towel to keep warm while you dip and heat the remaining tortillas.
Make 12 stacks of 2 tortillas each on a baking sheet. Divide the lamb evenly among the tortillas. Top with poblano strips, sprinkle evenly with the cheeses and bake 3 to 4 minutes, to melt the cheese and heat through. Serve immediately.
Note: Fresh chiles and bell peppers can be roasted over a gas flame or on a tray under the broiler. Keep turning so the skin is evenly charred, without burning and drying out the flesh. Transfer the charred peppers to a plastic bag, tie the top closed and let steam until cool to the touch, about 15 minutes. (If you are rushed, you can place the bag in a bowl of iced water to speed things up.) The best way to peel is just to pull off the charred skin by hand and then dip the peppers briefly in water to remove any blackened bits. Do not peel the pepper under running water since that will wash away flavorful juices. Once peeled, cut away stems, seeds and veins.
c.1997, M.S. Milliken & S. Feniger, all rights reserved