Preheat oven to 350°F. Spray mini muffin pan with vegetable pan spray.
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.
Bake 14 to 16 minutes or until light brown around edges. Remove from oven and immediately press the centers of the cookies with a small spoon (a measuring spoon works well), to make into a cup. Cool in pan for 10 minutes. Turn pan over and lightly tap the bottom to remove cookies. Cool completely on cooling grid.
For filling, microwave white chocolate at 50% power, stirring every 15 seconds, until melted and smooth. Cool slightly. With an electric mixer on medium speed, beat remaining butter and cooled chocolate until smooth. Beat in 3 tablespoons coffee liqueur and remaining 1/8 teaspoon salt. Gradually beat in 2 cups confectioners' sugar.
For glaze: whisk together remaining 1 cup confectioners? sugar and remaining 3 tablespoons coffee liqueur until smooth.
To assemble: spoon or pipe about 1 1/2 teaspoons filling evenly into each cookie. Drizzle with glaze.