Chicken and Black Bean Tostadas

Name: Chicken and Black Bean Tostadas
Ingredients: 1/4 cup canola oil, plus more for frying; 4 corn tortillas, preferably white; Kosher salt; 1 (15.5-ounce) can black beans, drained and rinsed; 1 teaspoon ground cumin; 1/4 cup low-sodium chicken broth; Freshly ground pepper; 1 clove garlic, minced; 1 tablespoon ancho chili paste or adobo sauce (from a can of chipotles in adobo); 1/4 cup fresh lime juice; 2 teaspoons brown sugar; 2 cups finely shredded green or red cabbage; 1 bunch radishes (about 6), julienned; 1/2 bunch fresh cilantro, roughly chopped; 1/2 cup sour cream; 1/2 rotisserie chicken, skinned and shredded into large pieces