In a medium bowl, combine flour, 1 teaspoon salt and baking soda; set aside. In a small bowl, stir together 2 tablespoons of coffee liqueur and instant espresso powder; set aside. In a large bowl, beat 1/2 cup butter, shortening and granulated sugar until light and fluffy with an electric mixer at medium speed. Beat in egg, coffee liqueur mixture and vanilla until mixed well. Add flour mixture and beat until just combined. Press dough into prepared pan, filling pan cavities 2/3 full.