Bah......
I make this every week.
Unsweetened butter
Romano cheese
Parmesan cheese
Heavy cream (36% milk fat) (double cream in the UK)
Nutmeg FRESH
Salt Kosher
Pepper FRESH ground
Ok, after you strain the pasta, DON"T run it under cold water, leave it hot.
Add the butter and grated cheese
Toss it till they are melted
Add the cream (optional - I prefer no cream)
Salt, pepper, nutmeg to taste