Japanese Chicken Meatballs
To prepare meatballs, heat a small skillet over medium-high heat. Add oil to pan; swirl to coat. Add mushrooms, 1 Tbs minced ginger, and 1 Tbs garlic; saute 2 minutes. Add sherry; cook 3 minutes or until liquid evaporates and mushrooms are tender. Remove from heat; cool. Place mushroom mixture and miso in a mini chopper; pulse 10 times or until very finely chopped.
Combine mushroom mixture, remaining 1.5 tsp minced ginger, remaining 1.5 tsp garlic, chicken, and next 6 ingredients (through egg white) in a bowl. Shape mixture into 36 (1-inch) meatballs.
Heat a saute pan over medium heat. Coat pan with cooking spray. Place meatballs in pan; cook 9 minutes, turning to brown on all sides.
Prepare sauce while meatballs cook. Combine mirin, soy sauce, sugar, and vinegar in a small saucepan. Bring to a boil; cook 3 minutes or until slightly thickened. Remove from heat; cool slightly. Stir in juice, 2 tsp grated ginger, and serrano. Reserve 2 Tbs sauce.
Drizzle sauce over cooked meatballs. Sprinkle with sesame seeds and any remaining sauce.