Bring a large pot of salted water to a rolling boil. Add spaghetti and cook for 8–10 minutes until al dente. Reserve 1/4 cup pasta water, then drain spaghetti.

In a large skillet, heat 1 tablespoon of neutral oil over medium-high heat. Add ground beef, breaking it apart, and brown for 5–7 minutes until fully cooked; drain excess fat.

Reduce heat to medium and add minced garlic and grated ginger. Sauté for 1 minute until fragrant.

Pour soy sauce, chili oil, brown sugar, and rice vinegar into the skillet, stir to combine and simmer for 2–3 minutes until thickened.

Add drained spaghetti to the skillet, toss using tongs. Pour in reserved pasta water if needed and continue tossing for 1–2 minutes until well combined.

Remove from heat and drizzle sesame oil over the pasta. Stir in chopped green onions and sprinkle sesame seeds if desired. Serve warm.