Cook pasta al dente according to package instructions. Drain and set aside. (While pasta is boiling, prepare shrimp sauce.)
Heat the butter in a large frying pan over medium heat. Add the onion and fry until transparent. Stir in the garlic and fry for 30 seconds until fragrant.
Quickly add in the sauce, stock powder, parsley, pepper and remaining salt. Allow the sauce to heat through for another minute before adding the milk (or cream). Continue cooking for a further minute or until the prawns are cooked through.
Add in the prawns with the basil and 1/2 teaspoon salt. Sauté shrimp for 2 minutes on one side then flip and continue to sauté on the other side for a further minute.
Once the pasta is cooked and drained, stir it through the creamy tomato sauce, toss until combined. Season with extra salt if desired.
Serve immediately with the optional parsley and/or parmesan sprinkled on top.