To make these tacos, start by making (or reheating) the barbacoa chuck roast. If you're using leftovers, simply reheat them on the stovetop or in the microwave until warmed through, then set aside.

Next, prepare the avocado-lime crema. Add the Greek yogurt, ripe avocado, cilantro, jalapeño, garlic, lime juice, and kosher salt to a blender and blend until smooth and creamy. If the crema is too thick, add a splash of water and blend again until you reach your desired consistency. Taste, adjust seasonings as needed, and set the crema aside.

Now, it's time to make the tacos. Preheat your oven to 375°F. Working with two baking sheets (or in batches with one), spray each sheet with avocado oil or brush it on lightly. Lay the corn tortillas out in a single layer on the prepared baking sheets, then spray or brush the tops lightly with avocado oil. Transfer the baking sheets to the oven and bake for 4 minutes.

Remove the trays from the oven and top each tortilla evenly with shredded barbacoa and a generous sprinkle of jack cheese. Return the trays to the oven and bake for another 7–9 minutes, or until the cheese is fully melted and the tortilla edges are nice and crispy.

Once done, remove the tacos from the oven. Drizzle the avocado-lime crema on top, then add the pickled onions and a sprinkle of fresh chives. Fold each tortilla in half to form a taco, and enjoy!