Chicken Tinga Tacos - Rick Bayless

Ingredients

• 2 ounces piloncillo (unrefined sugar) OR a generous ¼ cup dark brown sugar
• 1/2 cup vinegar (a fruit one like apple cider vinegar is typical in Mexico), plus more if needed
• 2 ounces (18 to 20 pieces) dried morita/chipotle colorado chiles, stemmed
• 3 garlic cloves, peeled and halved
• Salt
• Vegetable or olive oil to coat the pan
• 1 large white onion, sliced a little less than ½ thick
• 1 pound boneless skinless chicken thighs, cut into half-inch pieces
• 3 garlic cloves, peeled and finely chopped
• One 15 -ounce can diced tomatoes (preferably fire-roasted), lightly drained
• 3 to 4 pickled morita/chipotle chiles, thinly sliced, plus some of their pickling liquid OR 3 to 4 canned chilpotle chiles en adobo, thinly sliced
• About 1 teaspoon Mexican oregano
• A little additional vinegar, if you think the dish needs it
• 12 warm corn tortillas
• 1 ripe avocado
• About 3/4 cup (about 3 ounces) Mexican queso fresco or other fresh cheese like farmers cheese, mild feta or fresh goat cheese
• A handful of cilantro leaves for garnish