Melt the butter in a deep saucepan. Add the prawns and cook until pink. Remove from the pan and set aside in a bowl.
Add the flour to the pan and stir. Cook out for 1 minute and gradually add the milk, stirring constantly to prevent lumps.
Bring the base sauce to a simmer and add the spaghetti. Cook for 10 minutes (or as per packet instructions). Once the spaghetti has been cooked to al dente, add the pepper, salt and garlic powder. Stir and turn the heat down to low.
Now add the cream cheese, parmesan, parsley and chives. Stir then return the prawns to the pan. Stir to coat everything in the sauce then remove from the heat. Serve up with a generous topping of parmesan, chives and a squeeze of lemon.