Season the chicken. Add the shredded chicken, lime juice and the spices to a mixing bowl, and mix until well combined.
Make the sauce. Mix all of the listed ingredients in a small bowl. Refrigerate until ready to serve.
Bake the tortillas. Line two baking sheets with parchment paper. Lay tortillas out on the baking sheets in a single layer, without any edges overlapping. Spray lightly with olive oil. Mix the brown sugar and cumin in a small bowl and sprinkle over tortillas. Place in oven and bake for 10 minutes or until edges are turning dark brown.
Cook the beans. While the tortillas are baking, heat 2 tablespoons olive oil in a skillet over medium heat. Add the onion and saute for 3 minutes. Add the garlic and saute for 30 seconds. Add the beans and cook for 3 minutes. Using a potato masher, lightly mash the beans. Add the cumin, chicken broth, salt and pepper. Stir to combine. Cook for an additional 3 minutes. Keep warm.
Assemble the stacks. Place one tortilla on a tray or serving dish. Top with beans. Add another tortilla and top with chicken, avocado, pico and cilantro lime sauce. Repeat with remaining ingredients. Serve immediately.