Preheat oven to 375 degrees F and set a shallow 11 x 9 casserole dish on the countertop.
Heat a large sauté pan to medium heat and add olive oil. Turn pan to coat completely with olive oil. When oil is coating the pan, add onions. Cook, stirring, until onions are softened and translucent, approximately 3-4 minutes. Turn heat to low and add garlic, sea salt, chili powder, paprika and cumin. Cook another minute, stirring, then add diced tomatoes, tomato paste, chicken stock and coconut sugar. Stir to incorporate evenly, then add black beans and chicken. Cook, stirring, another two minutes until mixture is heated through.
Place tortilla chips in a food processor. Process until they form a crumble consistency. Or just crumble chips using your fingers.
Assemble Casserole: Spread 1/4 cup sweet potato cheese sauce on the bottom of the casserole dish. Top with a layer of 6-8 corn tortilla halves. Spread 2 cups chicken mixture over tortilla halves and pour over 1/2 cup cheese sauce. Top with 6-8 more tortilla halves and repeat this process in two more layers, using up the last of the cheese sauce. Spread crushed tortilla chips in an even layer over the top.
Bake casserole for 35 minutes, then allow to cool 5 minutes before serving. Top with optional garnish: olives, salsa, sour cream, cilantro, green onions, avocado, lime Casserole will keep tightly sealed in the refrigerator up to 5 days.