Heat the vegetable oil in a large pot over medium-high heat. Add the tomato paste, chili powder and cumin and cook, stirring, until the mixture darkens, about 1 minute. Add 1/2 cup water, the bell pepper, scallion whites and 1 teaspoon salt. Cook, stirring, until the bell pepper is crisp-tender, about 4 minutes. Add the turkey and cook, breaking up the meat with a wooden spoon, until cooked through, about 4 minutes.
Stir the tomatoes, chicken broth, beans and crushed tortilla chips into the pot; bring to a simmer. Partially cover and cook, stirring occasionally, until thickened, 10 to 12 minutes. Stir in all but a few tablespoons of the scallion greens and season with salt. Top with more crushed tortilla chips, sour cream, cheddar and the remaining scallion greens.
Photograph by Charles Masters
Courtesy of Food Network Magazine