Mexican Chicken Casserole

Name: Mexican Chicken Casserole
Ingredients: 2 tbsp. neutral oil; 1 medium yellow onion, chopped; 1 small jalapeño, stemmed, seeded, finely chopped (optional), plus more, thinly sliced, for serving; 2 cloves garlic, finely chopped; 3 c. shredded cooked chicken; 1 (15.5-oz.) can black beans, rinsed, drained; 1 (15.25-oz.) can corn, drained; 1.5 tsp. kosher salt; 1 tsp. chili powder; 1 tsp. ground cumin; 0.5 tsp. freshly ground black pepper; 1 (15-oz.) can fire-roasted tomatoes; 1 (10.5-oz.) can cream of chicken soup; 2 c. crushed tortilla chips, divided; 1.5 c. shredded cheddar, divided; 1.5 c. shredded Monterey Jack, divided