How to Make It
Prepare the Beans: Whisk together all ingredients in a large bowl until smooth.
Prepare the Chicken: Stir together ketchup, vinegar, mustard, onion powder, garlic powder, and salt in a saucepan over medium-high; bring to a boil. Reduce heat to medium, and simmer, whisking often to keep it from sticking, until slightly thickened, 8 to 10 minutes. Remove from heat. Add shredded chicken; toss to coat.
Preheat oven to 425°F. Spread bean mixture in an even layer in bottom of an 11- x 7-inch glass or ceramic baking dish. Arrange chicken mixture evenly over top of beans. Cover with aluminum foil, and bake in preheated oven until bubbly, 30 to 35 minutes. Uncover, and top evenly with cheese. Return to oven; bake at 425°F until cheese is melted, 3 to 5 minutes. Sprinkle with scallions; serve with corn chips.