Homemade Milano Cookies

1. Preheat the oven to 350°F. Line two baking sheets with parchment paper.

2. Make the cookies: In the bowl of an electric mixer fitted with the paddle attachment, cream the butter with the confectioners' sugar until light and fluffy, 4 to 5 minutes. Add the vanilla extract and mix to combine, about 1 minute.

3. Add the egg whites gradually, mixing until fully incorporated, 2 to 3 minutes. Add the flour and salt and mix just until incorporated, 1 to 2 minutes.

4. Transfer the batter to a 1-gallon ziplock plastic bag. Cut a ¼-inch opening at one of thebottom corners. Pipe the batter into lines 1½ inches long on the baking sheet, leaving at least 2 inches between each cookie. (Tip: Draw lines with a straight edge on the parchment paper, then turn the paper upside down and use the lines as a guide.)

5. Bake until the cookies are set and the edges are pale golden, 9 to 11 minutes. Remove from the oven and cool completely.

6. Make the Ganache: While the cookies cool, place the chocolate in a medium-size heat-safe bowl. In a small pot, bring the cream to a boil over medium heat. Pour the hot cream over the chocolate. Let it sit for 30 to 45 seconds, then stir to combine.

7. Assemble the Cookies: When the cookies are cool, turn half of them over and drop 1 tablespoon of the ganache onto the center of each upside-down cookie. Top with another cookie and press gently so that the ganache runs to the edges.

8. The cookies will keep at room temperature, stored in an airtight container, for up to two days.