Bring a large pot of salted water to a boil and cook the fettuccine until al dente, following the package directions.
Warm the cream cheese in the microwave for 20-30 seconds, repeating as needed, until very soft.
In a skillet over medium heat, combine the butter, softened cream cheese, cream, and minced garlic. Stir continuously as the butter melts and the cream cheese begins to incorporate into the mixture. For a smoother consistency, use a whisk.
Allow the sauce to gently simmer for 3-4 minutes, stirring occasionally, until it slightly reduces and thickens.
Mix in the grated Parmesan cheese and stir until fully melted and integrated, about 30 seconds. Remove the skillet from heat.
If the sauce appears too thick, add a small splash of the hot pasta water to loosen it before draining the pasta. Toss the sauce with the drained pasta and adjust seasoning with salt and pepper as desired.