In a bowl, whisk together 1/4 cup soy sauce, 1/4 cup packed brown sugar, 3 tablespoons rice vinegar, 2 tablespoons hoisin sauce and 1 tablespoon sesame oil until the sugar dissolves.

Add 4 minced garlic cloves and 1 teaspoon freshly minced ginger to the sauce and whisk to combine.

Heat a large skillet over medium-high heat and add 2 tablespoons vegetable oil; heat until shimmering, about 1 minute.

Add 1.5 pounds ground beef, season with 1/4 teaspoon salt and 1/4 teaspoon black pepper, and cook, breaking up the meat, until fully browned and crispy, about 5 to 7 minutes.

Carefully drain excess fat from the skillet and return the beef to the pan.

In a small bowl, whisk 2 tablespoons cornstarch with 3 tablespoons water until smooth to make a slurry.

Reduce heat to medium, pour the sauce over the beef and stir for 1 minute to heat through.

Stir in the cornstarch slurry and cook, stirring constantly, until the sauce thickens, about 30 seconds.

If desired, add 1/4 teaspoon red pepper flakes and simmer for 2 to 3 more minutes, stirring occasionally.

Garnish with 3 sliced green onions and 1 tablespoon sesame seeds and serve immediately over steamed rice or noodles.