Melt butter in a medium, non-stick saucepan over medium heat. Add cream cheese and garlic powder, stirring with wire whisk until smooth. Add milk, a little at a time, whisking to smooth out lumps. Stir in Parmesan and pepper. Remove from heat when sauce reaches desired consistency. Sauce will thicken rapidly, thin with milk if cooked too long. Toss with hot pasta to serve.