Prepare the spaghetti according to the package instructions.
In a small bowl, combine the sauce ingredients and set aside.
Meanwhile, in a wok or large frying pan on medium high heat, add 1 tablespoon cooking oil. Add ground beef and stir fry until cooked through. Remove the meat or push it to the sides.
Add the onion and cook for 2-3 minutes. Add garlic and cook for another 30 seconds, until fragrant.
Add the sauce. Meanwhile, in a small bowl, dissolve cornstarch in cool water to make a slurry. Once the sauce is bubbling, stir in the slurry and cook until the sauce starts to simmer and thicken. Stir in the ground beef.
Add the cooked and drained spaghetti and combine well. Turn off the heat. Add the green onion and cilantro. Drizzle with sesame oil and toss.