In a large Dutch oven, heat 2 tablespoons olive oil over medium-high heat. Add the chicken, chili powder and cumin. Season with salt and pepper and cook, stirring, for 5 minutes; transfer to a bowl.
In the same pot, heat the remaining 2 tablespoons olive oil. Add the apples and onion and cook, stirring, until softened, 6 minutes; add to the chicken.
In the same pot, melt the butter over medium-low heat. Whisk in the flour for 1 minute; whisk in the chicken broth and milk until thickened, 3 minutes. Stir in the chicken-apple mixture and beans, bring to a simmer, then stir in the cheese. Serve with the tortillas and scallions.