Preheat your oven to 450°F and line a baking sheet with foil or parchment paper. In a large bowl, combine the ground beef, chopped green onions, grated ginger, and minced garlic. Season generously with salt and pepper, then mix gently just until combined.

Roll the mixture into tablespoon-sized balls (you should get about 24-28 meatballs) and arrange them on one side of your prepared baking sheet. On the other side, toss the broccoli florets with 1 tablespoon olive oil, salt, and pepper. Bake everything for 15 minutes until the meatballs reach an internal temperature of 160°F and the broccoli develops crispy edges.

While everything bakes, heat the vegetable oil in a large skillet over medium-high heat. Add the soy sauce, brown sugar, garlic, ginger, water, rice wine vinegar, and red pepper flakes. Stir frequently and let it simmer for about 10 minutes, stirring occasionally to prevent sticking. You'll notice it darkening slightly and becoming fragrant as it reduces.

Whisk together the cornstarch and 1/2 cup water until completely smooth with no lumps, then pour it into your simmering sauce. Keep stirring for 2-3 minutes until the sauce thickens to a glossy, syrup-like consistency that coats the back of a spoon. Remove from heat.

Add your cooked meatballs to the skillet and gently toss until each one is completely coated in the sticky sauce. Serve the meatballs over steamed rice with the roasted broccoli on the side, then sprinkle with sliced green onions and sesame seeds.