• Preheat oven to 400℉ (200℃). Prepare your parchment paper and draw 2½ inch long lines, 3 inches apart as a guide for your cookies. Set the parchment paper, pencil side down, on a baking tray and set aside. I used two baking trays.
• Whisk together the flour, cornstarch, baking soda and salt to break up any clumps.
• In a bowl of your stand mixer fitted with the paddle attachment, beat the butter, granulated sugar and powdered sugar until pale, light and fluffy. Add the egg and vanilla then beat until just combined.
• Drop in the flour mixture and blend on low speed. Lastly, pour in the milk and mix until incorporated. The batter will be thick but runny enough to pipe easily. Transfer the batter into a piping bag fitted with a ½ inch piping tip or snip the end of a ziplock bag for a makeshift piping bag.
• Using the lines on your parchment paper as a guide, pipe straight lines onto the pan. Bake for 6-8 minutes or until the edges of the cookie have turned golden, rotating the pans halfway through for even baking. Leave to cool for 5 minutes then transfer to a wire rack to cool completely.

Make the ganache

• Heat the cream in a pot until it just reaches a simmer, nothing more. Pour the hot cream over the chopped chocolate and wait 5 minutes before stirring the ganache until smooth. Alternatively, place the cream and chocolate in a microwave safe bowl and heat on high in 30 second increments. If using the first method and the chocolate has not completely melted, follow the microwave method until the ganache is smooth.
• Transfer the ganache into a jar (uncovered) and cool until room temperature. Seal the jar and keep in the fridge to set the ganache further, around 15 minutes or more. Keep in the fridge until ready to use.

Assembly

• Pair the milano cookies to those with similar size then spread/pipe the ganache onto the cookie. Cover with the matching cookie pair. Repeat the process. Serve immediately and enjoy!