Preheat the oven to 450°F. Line a baking sheet with foil or parchment paper.

Add the ground beef, green onions, ginger, and garlic to a bowl. Season with salt and pepper. Mix gently with your hands until just combined - avoid overmixing to keep meatballs tender.

Roll the mixture into tablespoon-size balls, placing them on one side of the prepared baking sheet with space between each for even browning.

Add the broccoli florets to the other side of the baking sheet and toss with 1 tablespoon olive oil, salt, and pepper.

Transfer the baking sheet to the oven and bake for 15 minutes or until the meatballs are cooked through (browned outside, no longer pink inside) and the broccoli is tender with slightly crisp edges.

Meanwhile, in a large skillet, combine the vegetable oil, soy sauce, brown sugar, garlic, ginger, water, rice wine vinegar, and red pepper flakes. Stir and cook over medium-high heat for about 10 minutes, stirring occasionally.

Whisk together the cornstarch with 1/2 cup cold water until completely smooth. Add to your simmering sauce and continue to cook, stirring constantly, until the sauce thickens to a glossy consistency, about 1-2 minutes. Remove from the heat.

Add the cooked meatballs to the skillet of sauce and toss gently until the sauce completely coats each meatball.

Serve the meatballs and remaining sauce over bowls of steamed rice, topped with sliced green onions and sesame seeds. Serve the roasted broccoli on the side.