- Preheat oven to 425°F.
- Coat a baking sheet with cooking spray.
- Mash rinsed black beans and cumin with a fork in a large bowl until no whole beans remain.
- Stir in corn and 1/4 cup breadcrumbs.
- Combine chopped tomatoes, sliced scallions, chopped cilantro, 1/2 teaspoon chili powder and salt in a medium bowl.
- Stir 1 cup of the tomato mixture into the black bean mixture.
- Mix the remaining 1/3 cup breadcrumbs, oil and the remaining 1/2 teaspoon chili powder in a small bowl until the breadcrumbs are coated with oil.
- Divide the bean mixture into 8 scant 1/2-cup balls.
- Lightly press each bean ball into the breadcrumb mixture, turning to coat. Place on the prepared baking sheet.
- Bake the croquettes until heated through and the breadcrumbs are golden brown, about 20 minutes.
- Stir sliced avocado into the remaining tomato mixture.
- Serve the salsa with the croquettes.