Prepare the stir-fry sauce by whisking soy sauce, brown sugar, grated ginger, and minced garlic together in a bowl. Create a cornstarch slurry by mixing cornstarch and water in a separate small bowl.

Chop all desired vegetables including broccoli florets, sliced carrots, and a sliced bell pepper.

Heat olive oil in a large skillet or wok over medium-high heat, then brown the ground beef, breaking it up as it cooks; drain excess fat.

Add the chopped broccoli, carrots, and bell pepper to the skillet with the beef and stir-fry for 5-7 minutes until they are tender-crisp.

Pour the prepared soy sauce mixture into the skillet, bring to a simmer, then stir in the cornstarch slurry and cook until the sauce thickens.

Remove the stir-fry from heat, stir in sesame oil, and garnish with sliced green onions before serving.