Preheat oven to 350°. In a small bowl, combine the beans, onion, green chiles and cumin. Place 8 crackers in an 8x4-in. loaf pan coated with cooking spray. Top with half of the bean mixture; layer with remaining crackers and bean mixture. Sprinkle with cheese.
In a small bowl, combine the milk, mayonnaise and egg; pour over cheese. Bake, uncovered, until a thermometer reads 160°, 20-25 minutes. If desired, serve with sour cream and olives.