In a large pot, heat water over high heat until boiling. Add salt to season the water. Once it is boiling, add fettuccine and cook according to package instructions.
In a large pan, heat butter over medium heat. Add minced garlic and cook for 1 to 2 minutes. Stir in double cream.
Let double cream reduce and cook for 5 to 8 minutes. Add half of the parmesan cheese to the mixture and whisk well until smooth. Keep over heat and whisk well until cheese is melted.
Toss alfredo sauce with fettuccine pasta and add half of the parmesan cheese. Once it is tossed, garnish with the remaining parmesan cheese and chopped parsley.