Cook the pasta: Boil spaghetti in salted water according to the package instructions. Drain and set aside.

Stir-fry the vegetables and sausage: In a frying pan, heat butter or oil. Add sausages, onion, carrot, and green pepper. Stir-fry until softened.

Add ketchup: Add the cooked spaghetti to the pan, then add ketchup and soy sauce. Mix well and stir-fry for another 1–2 minutes.

Serve: Plate the pasta and sprinkle with dried parsle