Bring a large pot of lightly salted water to a boil. Break pasta into small pieces and add to boiling water; cook for 8 to 10 minutes or until al dente; drain. In a large bowl, toss together the pasta, cabbage, carrots, green, red and yellow capsicums, 1/2 of the coriander, 1/2 of the onions and prawns.
In a small bowl, stir together the peanut butter, tahini, rice wine vinegar and sweet chilli sauce. Season with soy sauce, sesame oil, brown sugar, garlic powder, salt and pepper. Ten minutes before serving, toss the sauce with the cabbage mixture until evenly coated. Garnish with remaining coriander, spring onions, peanuts and black sesame seeds.