Mix dry ingredients; set aside. Beat butter, shortening, and sugar until fluffy. Add eggs and vanilla, mix well. Incorporate dry ingredients in two batches. Chill dough for 30 minutes. Roll to 3/8-inch thickness, cut into circles, and bake at 350°F for 8-10 minutes. Cool completely before frosting.
Notes
Ensure frosting ingredients are at room temperature for best results.