easy black bean burger

Ingredients

• 3 cups cooked black beans, drained and rinsed
• ⅓ cup grated yellow onion*, (about ½ medium)
• 2 garlic cloves, minced
• 2 chipotle peppers from a can of chipotles in adobo, diced
• 2 tablespoons adobo sauce
• 1 tablespoon tamari
• 1 tablespoon balsamic vinegar
• 1 teaspoon ground cumin
• ½ teaspoon sea salt
• ½ teaspoon freshly ground black pepper
• 1 large egg**
• 1 cup panko bread crumbs
• Extra-virgin olive oil, for brushing
• Cooking spray, if grilling
• Hamburger buns, for serving
• Desired fixings, for serving