Preheat oven to 350℉.
Place 1 can of beans and ½ cup broth in a blender or food processor; blend until thick and saucy, about 10 seconds.
Heat 2 tablespoons oil in a medium pan over medium heat; add ½ medium onion, 1 teaspoon cumin, ½ teaspoon oregano, ½ teaspoon paprika and ¼ teaspoon salt; cook, stirring frequently, for 3 minutes. Add 8 ounces mushrooms; cook, stirring frequently, until the mushrooms begin to release their liquid, about 2 minutes. Add the pureed beans and simmer, stirring frequently, until thickened slightly, about 5 minutes.
Place tortillas on a microwave-safe plate. Microwave on High until the tortillas are pliable, about 1 minute.
Spread ¼ cup enchilada sauce on the bottom of a 9-by-13-inch casserole dish. Add about ⅓ cup black bean filling to each tortilla; roll and assemble, seam-side down, tightly in the casserole dish.
Pour the remaining ¾ cup enchilada sauce over the enchiladas, spooning the sauce onto the tortillas so they're completely covered. Top with ½ cup cheese. Cover with foil and bake until melted and bubbly, 25 to 30 minutes. Serve with avocado and ¼ cup chopped cilantro.
