Combine ground chicken, minced garlic, grated ginger, chopped green onions, egg, panko breadcrumbs, soy sauce, sesame oil, and black pepper in a large bowl. Mix gently with your hands until just combined, being careful not to overwork the meat. Roll the mixture into about 20 evenly sized balls, roughly the size of golf balls.

Whisk together mayonnaise, soy sauce, rice vinegar, sesame oil, grated ginger, chili flakes, and honey in a small bowl until smooth and creamy. Set aside until ready to serve.

Heat a large skillet or Dutch oven over medium-high heat with a light coating of oil. Place meatballs in a single layer and cook undisturbed for 4 to 5 minutes on the first side until golden brown. Turn and cook for another 4 to 5 minutes on the other side, turning occasionally until cooked through, about 12 to 15 minutes total.

While the meatballs finish cooking, whisk together soy sauce, honey, rice vinegar, cornstarch, and water in a small saucepan. Bring to a simmer over medium heat, stirring occasionally. The glaze will thicken in about 2 to 3 minutes. It should be thick enough to coat the back of a spoon but still pourable.

Pour the warm teriyaki glaze over the cooked meatballs in the pan. Gently toss to coat evenly and let cook for 1 to 2 minutes more so the glaze caramelizes slightly on the outside.

Transfer meatballs to a serving bowl and drizzle generously with the sesame ginger cream sauce. Sprinkle the top with fresh sliced green onions and toasted sesame seeds. Serve immediately while warm.