Bring a pot of well-salted water to a boil and cook the fettuccine until al dente
In a bowl, add the cold cubed butter
Drain the pasta and immediately transfer it to the bowl
Add a ladle of hot pasta water and start tossing with tongs or by shaking the bowl until the butter melts
Once the butter is fully melted, add the Parmigiano little by little, continuing to toss until a smooth, creamy sauce forms
Add more pasta water if needed
Plate and finish with extra Parmigiano if desired
