Create a template on one piece of parchment paper with 2" lines. You'll place this underneath the other pieces of parchment paper as a guide for piping the batter.

In a large bowl, cream together the butter, powdered sugar, salt, and vanilla until light and fluffy.

Add the egg and egg whites and beat on high speed until fully combined.

Add the flour and mix on low speed until just combined.

Transfer batter to a piping bag with a ½" round piping tip.

Place the template on a baking sheet and another piece of parchment paper on top. Pipe the batter onto the 2" lines. To smooth out the pointed ends, dip a finger in water and gently pat them down.

Place the baking sheets in the fridge for at least 20 minutes. This prevents the cookies from spreading too much!

Meanwhile, preheat the oven to 350 degrees F.

Bake the Milano cookies, one baking sheet at a time, for 8-10 minutes or until just barely golden brown on the edges. Allow them to cool completely on the baking sheet.

In a small saucepan, bring the heavy cream to a simmer, or about 190 degrees F.

Add the chocolate, then place a plate on top for one minute. Remove the plate, then stir with a rubber spatula until smooth.

Stir in the mint extract, then transfer to a piping bag with a small round piping tip. Place the piping bag in the fridge until the ganache has firmed up to a pipe-able consistency.

Assemble the Milano cookies with the mint chocolate ganache. Enjoy immediately or place in the fridge to crisp up like a store-bought Milano cookie!