Bring a large pot of salted water to a boil. Add spaghetti and cook according to package directions until al dente, about 8–10 minutes. Reserve 1/4 cup of pasta water, drain spaghetti, and set aside.

In a skillet or wok, heat 1 tablespoon of oil over medium-high heat. Add the ground beef and cook for about 5–7 minutes until browned. Drain excess fat if needed.

Lower heat to medium, add minced garlic and grated ginger. Sauté for about 1 minute until fragrant, being careful not to burn.

Add soy sauce, chili oil, brown sugar, and rice vinegar to the skillet. Stir and simmer for 2–3 minutes until the sauce thickens slightly.

Add the drained spaghetti to the sauce, tossing to coat. If too thick, add reserved pasta water gradually until desired consistency.

Turn off the heat, drizzle with sesame oil, toss in the green onions, and sprinkle sesame seeds on top before serving.