In 4-quart saucepan, melt 2 tablespoons of the butter over medium-low heat. Add flour; cook 2 minutes, stirring constantly with whisk. Slowly pour hot milk and hot whipping cream into butter-flour mixture; beat with whisk until smooth. Increase heat, and heat to boiling, beating constantly, 1 to 3 minutes or until thickened. Remove from heat. Stir in shredded Gruyère cheese and 1/3 cup of the shredded Parmesan cheese until smooth. Stir in salt, 1/4 teaspoon of the pepper, the garlic powder and nutmeg until combined.