In a saucepan combine heavy cream, butter and cream cheese. Bring to a simmer over medium high heat, then keep it simmering until all is melted and mixed well. Stir often!
Right after the mixture comes to a light boil, whisk in the Parmesan cheese and garlic powder.
Simmer this for 5-10 minutes on medium-low heat, just until it thickens enough to coat a spoon.
Salt and pepper to taste.