Press 3/4 teaspoon pepper into meaty sides of chicken breast halves. Combine 1/3 cup melted butter and 1/4 cup chopped basil; stir well. Brush on chicken lightly.
Combine 1/2 cup softened butter, 2 tablespoons basil, Parmesan cheese, garlic powder, salt and pepper in small bowl. Beat at low speed of an electric mixer until mixture is well blended and smooth. Transfer to a small serving bowl; set aside.
Grill chicken on medium coals 8-10 minutes per side, basting frequently with remaining melted butter mixture.
Serve grilled chicken with basil-butter mixture. Garnish with fresh basil sprigs, if desired.