Method

• 1.
  Place butter in a frypan over medium heat and cook, shaking the pan occasionally, for 5 minutes or until nut brown and fragrant. Transfer to a bowl and chill until set, then remove from fridge and bring to room temperature.

• 2.
  Preheat oven to 180°C/160°C fan-forced and line 2 baking trays with baking paper.
• 3.
  Using handheld electric beaters, beat butter and sugar together until pale. Fold in flour, baking powder and milk powder, then add bourbon, eggs and chocolate buttons, and beat until combined. Roll into 16 even balls and press down slightly to flatten.
• 4.
  Arrange cookies on baking trays, leaving 4cm between each. Bake, swapping trays halfway, for 18-20 minute, until light golden and just firm to the touch. Transfer to a wire rack to cool.
• 5.
  For the frosting, using clean handheld electric beaters, beat butter, icing sugar and bourbon together until pale. Add white chocolate and beat to combine, then chill for 20 minutes to stiffen. Spread frosting over flat side of half the cookies, then sandwich with remaining cookies to serve.