Preheat oven to 425 degrees. Line a baking sheet with parchment paper.
Fill a large skillet with high sides with water. Bring to a boil.
While the water comes to a boil, mince the garlic and ginger. Slice the red bell pepper. Cut the small onion in half and dice. Reserve the rest of the onion to grate over the chicken meatball mixture. Slice the green onion.
Add 2 tablespoons soy sauce, 1 tablespoon sesame oil, 2 teaspoons ginger, 2 garlic cloves, and egg to the bottom of a medium bowl. Whisk to combine. Add the ground chicken, panko, 1/4 cup of the green onion, and 1/4 teaspoon salt. Grate the remaining half of the onion on top. Use your hands or a fork to combine the chicken mixture just until it's combined. The mixture will be very sticky and wet, this is normal.
Spray a small ice cream or cookie scoop with non-stick cooking spray. Portion the meatballs out into heaping tablespoon portions. Get hands slightly wet and roll the chicken into uniform meatballs.(Getting your hands slightly wet will prevent the chicken meatballs from sticking to your hands.) Line on prepared baking sheet. Place in the oven and bake 10-12 minutes until golden brown and cooked through.
While the chicken meatballs cook, make the orzo. Right after putting the meatballs in the oven, drop the orzo into the boiling water.
Add the remaining tablespoon soy sauce to a small bowl along with the hoisin, peanut butter, chicken stock or water, and red pepper flakes. Stir to combine. Set aside.
When the orzo is aldente, drain in a colander and return the empty pot to the stove over a medium heat. (Let the orzo rest in the colander.) Add the remaining tablespoons of sesame oil to the pot. When the oil is hot, add the chopped onion and red bell pepper. Saute until slightly softened, about 3-4 minutes. Add the garlic and ginger, cook another 1-2 minutes. Add the baby spinach and toss until slightly wilted. Turn the heat on low and add the cooked orzo along with the sauce. Toss to combine. Season with salt and pepper.
When the chicken meatballs are done cooking, spoon the orzo on to plates or bowls. Top with meatballs. Sprinkle with extra green onion and sesame seeds.