Mushroom Quinoa Burger with Special Sauce

Ingredients

• 1 large portobello mushroom, gills removed, roughly chopped
• 1 cup canned black beans, rinsed
• 2 tbsp almond butter
• 3 tbsp mayonnaise or plant-based alternative, divided into 1 tbsp and 2 tbsp
• 1 tsp ground pepper
• ¾ tsp garlic powder, divided
• ½ tsp salt
• ½ cup cooked quinoa
• ¼ cup rolled oats
• 1 tbsp ketchup
• 1 tsp Dijon mustard
• 1 tbsp olive oil
• 4 whole-wheat hamburger buns