Bring a large pot of salted water to a rolling boil. Add spaghetti and cook until al dente, about 8–10 minutes. Reserve ¼ cup of pasta water before draining.

In a large skillet, heat oil over medium-high heat. Add ground beef, breaking it apart as it cooks for about 5–7 minutes until browned.

Lower heat and add minced garlic and grated ginger. Sauté for 1 minute until fragrant.

Stir in soy sauce, chili oil, brown sugar, and rice vinegar. Simmer for 2–3 minutes until the sauce thickens slightly.

Add reserved cooked spaghetti to the skillet, tossing gently until noodles are coated. Add reserved pasta water as needed for desired consistency.

Remove from heat and drizzle with sesame oil. Toss in chopped green onions and optional sesame seeds. Serve immediately.