Add the cream cheese, butter, milk, and heavy cream to a medium saucepan over medium heat. Whisk together until everything is melted and well combined, about 6 minutes.
Bring to a slight boil then reduce heat to medium-low and whisk in the Parmesan, garlic, 1/8 tsp salt, and 1/4 tsp fresh ground pepper until well combined.
Simmer over medium-low heat, stirring often, until thickened, 10 to 15 more minutes. Take off the heat and season with additional salt & pepper if necessary.