Heat oven to 400° F. Heat oil in a large, lidded nonstick skillet over medium heat. Add onion and cook 5 minutes. Stir in garlic and cook an additional minute. Add ground chicken and increase heat to medium-high. Stir in chili powder, salt and cumin and cook for 6 to 7 minutes.
Stir in diced tomatoes and tomato paste. Cover and simmer over low heat for 5 minutes.
Meanwhile, arrange half of the tortilla chips on an oven-safe platter or rimmed baking sheet. Spoon half the chicken chili over chips and top with 3/4 cup of the cheese. Repeat layering. Bake at 400° F for 8 minutes or until cheese has melted. Garnish with jalapeños, sour cream, guacamole, tomatoes and cilantro, if desired.