- 8 garlic cloves
- ¼ to 1/3 cup ground guajillo or ancho chile (available from national companies like McCormick, Mexican groceries or internet sites)
- ½ teaspoon ground cumin
- 1 teaspoon ground black pepper
- 3 tablespoons vinegar (cider vinegar is common in Mexico)
- 6 medium (about 1 ½ pounds) red-skin boiling or Yukon gold potatoes, each cut into 6 wedges
- A 3-pound bone-in lamb (or goat) shoulder roast
- 1 15-ounce can diced tomatoes in juice (preferably fire-roasted)
- 1 teaspoon dried oregano, preferably Mexican
- About ½ cup finely chopped white onion, for garnish
- ½ cup chopped cilantro, for garnish
- 1 lime, cut into 6 wedges
- Cut a slit in the side of each garlic clove, place them into a microwaveable bowl, cover with plastic, poke holes in the top and microwave for 30 seconds at full power. Cool until handleable and slip off the papery husks. One by one, drop the garlic cloves into a running food processor, letting each get thoroughly chopped before adding the next. Measure in the chile powder, cumin, black pepper, vinegar, 1 teaspoon salt and ½ cup water.
- Spread the potatoes over the bottom of a slow-cooker. Sprinkle generously with salt. Lay the meat on top. Scrape the marinade onto the meat, then spread it sloppily over the top and sides, letting some fall onto the potatoes. Pour enough water into the slow-cooker to cover the potatoes and the lower ¼ inch of the meat. Cover and slow-cook for 6 hours until the meat is fall-off-the-bone tender (the dish can hold on a slow-cooker’s “keep warm” function for 4 more hours or so).
- Carefully remove the tender meat to a large plate, pulling out the bone and cutting away any visible gristle or fat. Use a slotted spoon to scoop the potatoes onto the plate with the meat. Keep warm in a low oven. Spoon off the fat that has risen to the top of the broth.
- Set a medium (3- to 4-quart) saucepan over medium-high heat and pour in the tomatoes with their juice. Cook, stirring frequently, until the juice has reduced to the consistency of tomato paste. Tip or ladle the broth from the slow-cooker into the pan. Add the oregano and bring to a boil. Taste and season with salt, usually about 1 ½ teaspoons.
- Divide the potatoes between 6 deep dinner plates (or wide bowls). Coarsely shred the meat and distribute between the plates. Ladle a portion of broth over each one, then sprinkle generously with chopped onion and cilantro. Pass the lime wedges separately for each person to squeeze on to his or her own liking—an essential part of great birria.