In a saucepan over medium heat, melt together the butter, cream, half-and-halfs, and cream cheese. Add the garlic powder and parmesan; whisk to combine and simmer over medium-low heat until slightly thickened. Pour into blender and add basil. Blend until basil is thoroughly combined and sauce is green. Remove back to saucepan and re-heat on the stove (sauce will have lost heat through blending). If it seems too thick, add more cream to thin it. Serve with your favorite pasta.