Cook pasta according to pack directions, but do not add salt.
While pasta is cooking, prepare marinade. In a large bowl, combine garlic, jalapeno pepper, soy sauce, stock, sugar and chilli powder. Add beef, toss to coat well.
Spray a large non-stick frying pan with vegetable oil cooking spray. Add geef and marinade to the pan, stir-fry over a medium-hight heat until browned, about 5 minutes.
In a large bowl, whisk together vinegar, grape juice, sesame oil and sesame seeds. Drain pasta in a colander. Add pasta and steak to bowl, toss to coat. Divide among individual dinner plates. Sprinkle wtih chives. Serve.