The Night Before: Rub the outside of the pork shoulder with the ground cumin. Season liberally on all sides with kosher salt and freshly ground black pepper. Place the pork shoulder, with the fat cap facing up, in a 4-quart slow cooker. Add the orange juice, sliced onion, diced jalapeño peppers, garlic cloves, and bay leaf. Cover and cook on low for 10 to 12 hours, or until the meat is very tender and begins to fall off the bone. See notes for prepping tips.
Before Serving: Make the mini tortilla cups: Preheat the oven to 375°F (190°C) with a rack in the center position. Set aside two 12-cup muffin tins (if you only have one muffin tin, you will need to make the tortilla cups in batches).
Warm the corn tortillas until they are pliable. Stack 6 tortillas at a time. Use a biscuit cutter, mug, or small bowl (4-inches in diameter) as a guide, cut the corn tortillas into 4-inch-diameter circles. Discard the scraps. Spray both sides of the tortilla discs with cooking spray. Gently press each disc into the cups of the muffin tin, and sprinkle them lightly with salt. If the tortillas crack or tear, it is because they have not been warmed sufficiently. Bake for 12 to 18 minutes, rotating the pan halfway through, or until the tortilla cups are completely crisp and golden brown. Allow them to cool before removing.
Preheat the broil to high and set an oven rack about 4 to 5 inches below the broiler element. Once the pork is tender (and nearly falling apart), use two forks to shred it. Discard any large pieces of fat and bay leaf. Use a large slotted spoon to transfer the meat and any onions/garlic cloves to a half sheet pan. Spread into a thin layer. Drizzle the meat with the tablespoon of olive oil. Place the sheet pan under the broiler for 3 to 7 minutes – watching carefully – or until the carnitas are crispy and caramelized. Remove from the oven and allow to cool slightly.
Before serving, fill the tortilla cups with carnitas, top with a spoonful of guacamole, and garnish with chopped onion and chopped cilantro. Serve immediately with lime wedges.
Tips for Success:
To save time on the big day, prep and cook the carnitas the night before you wish to serve this dish.
Prep and turn on the slow cooker and let it run overnight (if you feel comfortable). You’ll wake up to the smell of carnitas cooking in your kitchen and 99% of the work for this recipe will be done ahead of time.