Prepare tomatillo salsa by placing tomatillos, garlic, onion, jalapeño, cilantro, and vegetable broth in a blender or food processor. Blend until smooth. Transfer to saucepan and add 1 tablespoon olive oil. Cook until tomatillo sauce changes color to olive green about 5 to 6 minutes.
Preheat oven to 350°F.
Heat oil in medium non-stick skillet over medium high heat. Add red onions and garlic and cook for 1 to 2 minutes until lightly brown. Add corn kernels, black beans and salt. Stir frequently until cooked evenly. Remove from heat.
Warm tortillas for 10 to 15 seconds on each side on an ungreased pan.
Place corn/bean mixture evenly along center of each tortilla and fold. Place in oven safe platter seam side down. Top enchiladas with salsa and cotija cheese. Bake for 8 to 10 minutes. Serve with shredded napa cabbage and sour cream.