Preheat broiler with oven rack in upper middle position.
Heat oil in a large cast-iron skillet over medium-high. Add 1/2 cup onion and jalapeño to pan; sauté 4 minutes or until tender. Add flour, cumin, and chili powder; cook 1 minute, stirring constantly. Add stock; bring to a boil. Reduce heat to medium, and stir in crumbled beef patties and beans; cook 2 minutes. Stir in mozzarella; cook 1 minute or until cheese is melted. Remove pan from heat.
Sprinkle Mexican-blend cheese over pan; broil 1 minute or until cheese is melted. Sprinkle remaining 1/4 cup red onion, tomato, and avocado over pan. Serve with chips.