Whisk together both flours, baking powder, coffee and salt.

Beat butter and sugar on medium-high speed until light and fluffy. Add egg yolks, and beat until combined, scraping down sides of bowl as needed. Add flour mixture in two - three batches, alternating with the irish cream. Once the dough forms, remove it from the bowl and gather into a ball.

On a lightly floured work surface, roll out the dough. Using a lightly floured round cookie cutter, cut out rounds and place about 1 inch apart on a sheet pan lined with parchment. Bake for 15- 18 minutes. Transfer to a wire rack to cool completely.

In a medium bowl,beat the egg yolks until light in color, using a hand mixer.

In a small pan combine lemon juice, sugar and the corn syrup. Mix with a silicon spatula until the sugar looks moist. Place over medium-high heat and keep stirring until the sugar dissolves and the syrup begins to boil. Allow the syrup to come to full boil without stirring it too much. Remove from heat.

While the syrup is still hot, beat it into the egg yolks. Allow a steady thin stream of sugar syrup to fall into the yolks while you beat the mixture with the hand mixer. Once all the sugar syrup is added, continue to beat until the mixture thickens.

Allow to cool down completely, before adding in the butter. Once cool, add to a the bowl of a stand mixer and in the butter, the irish cream and the powdered sugar. Beat until all the butter is mixed in a and your butter cream looks smooth and shiny.

Take a spatula and spread filling onto flat sides of half the cookies. Sandwich with remaining cookies, keeping flat sides down.