Pistachio Macarons

For the ganache filling:

Combine the cream and corn syrup in a small, heavy-bottomed saucepan and bring to a simmer over medium heat. Whisk in the pistachio paste. Combine the butter and white chocolate in a heatproof bowl, pour the cream mixture over them, and whisk to combine. Pour into a small bowl and refrigerate for 24 hours.

For the cookie:

Line two baking sheets with parchment paper. Sift the powdered sugar and almond flour into a bowl and set aside.

Put the egg whites in a medium mixing bowl. Use an electric hand mixer to whisk the egg whites until they foam. Add the cream of tartar. While beating continually, slowly pour in the granulated sugar. Beat until stiff peaks form. Add the vanilla extract and green food coloring until the desired color is reached.

Gently fold in the dry ingredients in four increments. Spoon the mixture into a piping bag fitted with a 1/2-inch round tip. Pipe rounds about 1¼ inches in diameter onto the baking sheets, leaving 1½ inches between them. Let sit at room temperature to dry until the tops are no longer sticky to the touch, approximately 30 minutes to one hour.

Preheat the oven to 300°F. Bake the macarons for 12 minutes, until they have puffed out. Rotate the baking sheets and bake for another six minutes. Place the baking sheets on wire racks and let the cookies cool completely before removing.

To assemble:

Using a piping bag fitted with a 1/2-inch round tip, pipe the ganache onto the bottom of half of the cookies. Top with the other half of the cookies to form a macaron. The macarons will keep for about one week in a tightly sealed container at room temperature.