Preheat the oven to 350°F and coat a 9×13 baking dish with cooking spray.
In a medium mixing bowl, break the ground beef into small pieces. Toss with the beaten egg, plain bread crumbs, minced garlic and onion and Kosher salt.
Roll the ground beef mixture into 1 ¾ inch balls, placing into prepared baking pan. You should have about 20 meatballs.
Bake the meatballs for 20 minutes. Remove.
In a medium saucepan over medium heat, combine the light brown sugar, ketchup, white vinegar, soy sauce, ground ginger and 1 1/4 cup water, whisking until smooth. Bring to a low simmer.
Meanwhile, whisk together the cornstarch and remaining ¼ cup water until smooth. Whisk into the sauce and continue to simmer until sauce thickens, becomes a deep brown and is glossy. Simmer on low for 3-4 minutes to reduce slightly.
Add the meatballs, draining and discarding from any excess fats and liquids in the pan.
Simmer on low heat with meatballs for 25 minutes, stirring every 5 minutes.
Garnish with the sesame seeds and scallions.
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