Rinse 1 cup of quinoa thoroughly under cold water. In a medium saucepan, combine rinsed quinoa and 2 cups chicken broth. Bring to a boil, then reduce heat to low, cover, and simmer for 15-20 minutes, or until all liquid is absorbed and quinoa is fluffy. Set aside.

Preheat oven to 375°F (190°C). Heat 1 tbsp olive oil in a large skillet or Dutch oven over medium-high heat. Season chicken cubes with 1/2 tsp salt and 1/4 tsp black pepper. Add chicken to the skillet and cook for 5-7 minutes, stirring occasionally, until browned on all sides and cooked through. Remove chicken from skillet and set aside.

In the same skillet (no need to clean), add another 1 tbsp olive oil if necessary. Add chopped onion and cook for 3-5 minutes until softened. Add minced garlic, minced chipotle peppers, and adobo sauce; cook for 1 minute until fragrant.

Stir in diced tomatoes (undrained), tomato paste, cumin, chili powder, dried oregano, smoked paprika, and sugar. Bring to a simmer and cook for 5-7 minutes, allowing the sauce to thicken slightly. Stir in 1/2 tsp salt.

To the skillet with the sauce, add the cooked chicken, cooked quinoa, rinsed and drained black beans, and drained corn. Stir gently to combine everything thoroughly.

Transfer the entire mixture to a 9x13 inch baking dish, spreading evenly. Sprinkle 1 cup of shredded cheese over the top of the casserole.

Bake for 20-25 minutes, or until the casserole is heated through and the cheese is melted and bubbly.

Remove from oven. Sprinkle with the remaining 1/2 cup shredded cheese and let it melt for a few minutes from the residual heat (or return to oven for 2-3 minutes if needed). Garnish with fresh chopped cilantro, sliced avocado, and a dollop of sour cream or Greek yogurt, if desired. Serve hot.