2tablespoonsunsalted butter1/4 stick, at room temperature and cut into cubes
Directions for the Ganache
Place the dark chocolate chips in a large bowl.
Warm the cream in a small saucepan over medium heat until it just starts to boil.
Stir it into the chocolate without creating bubbles.
Let sit for 1 minute. Add the butter and stir until smooth.
Chill in the refrigerator until thickened but still spreadable, about 30 minutes.
You will need a pastry bag fitted with a 1/2-inch tip. If you don’t have one, you can either spoon round dollops of batter onto the baking sheet or make a pastry bag by snipping off one corner of a large resealable plastic freezer bag.
Directions for macaroons
Preheat oven to 350°F.
Line 2 large baking sheets with parchment paper.
Place the powdered sugar, almond flour, cocoa powder, and salt in a food processor fitted with a blade attachment and pulse several times. Process until fine and combined, about 30 seconds.
Sift through a flour sifter into a large bowl; set aside.
Place the 3 egg whites in the clean bowl of a stand mixer fitted with a whisk attachment. Beat on medium speed until opaque and foamy, about 30 seconds. Now add a pinch of cream of tartar, increase the speed to medium high, continue to beat until the egg whites are white in color and hold the line of the whisk, about 1 minute.
Continue to beat, slowly adding the granulated sugar, until the sugar is combined, the peaks are stiff, and the whites are shiny, about 1 minute more. Do not over whip. Transfer the meringue to a large bowl.
Take a rubber spatula, and now gently fold the dry mixture with the egg whites in four different scoops until the dry ingredients are just combined.
Bake cookies, 1 sheet at a time, until firm to touch in center and dry and cracked on top, about 7 minutes pull the pan put and then rotate and bake for another 7 minutes.
Arrange 1 macaroon, flat side up, on work surface. Drop 1 scant tablespoon filling onto cookie.
Top with second macaron, flat side down.
Press lightly to adhere, making sandwich.
Repeat with remaining macarons and filling. Arrange macarons on platter.
Cover; chill at least 2 hours and up to 1 day.
IMPORTANT Slide parchment with cookies onto work surface; cool cookies. Repeat with remaining batter, cooling sheets completely and lining with clean parchment for each batch.