This delightful French cookie is crisp on the outside with a silky ganache filling that will momentarily transport you to the streets of Paris.
Position a rack in the middle of oven and preheat to 400°F. Line two large baking sheets with parchment paper.
In a food processor or large bowl, gently pulse or combine the almond meal, icing sugar, and cocoa powder until well blended.
In the bowl of an electric mixer, beat together egg whites and salt on medium-high speed just until the whites form soft peaks when the beaters are lifted. Add the sugar and beat just until the whites form stiff peaks when the beaters are lifted. Using a spatula, gently fold in the almond mixture.
Transfer the batter to a pastry bag fitted with a 1/2" plain tip. Pipe 1"-diameter mounds about 2" apart on the prepared baking sheets.
Bake, one sheet at a time, until the tops appear dry but macarons are still slightly soft to the touch, 6-8 minutes
Transfer cookies (still on parchment paper) to slightly damp kitchen towels and let cool for a few minutes before carefully peeling the macarons from the paper and transferring to wire racks to cool completely.
In a saucepan over high heat, bring cream just to a boil. Remove from heat and whisk in cocoa powder; add chocolate, and butter and whisk until smooth. Let cool to room temperature, then cover and refrigerate until filling is firm enough to hold its shape when spread, about 30-60 minutes.
Transfer the filling to a pastry bag fitted with an 1/2" plain tip, or fill a zip-top plastic bag with filling and make a small cut in one corner. Pipe the filling generously on the flat side of half the macarons. Top with remaining macarons, flat side down, pressing gently together to form sandwiches.
Macaron cookies can be made up to 1 day in advance and stored in layers separated by wax paper in an airtight container.
Finished cookies can be stored in layers separated by wax paper in an airtight container in the fridge for up to 2 days.
Adapted from: Williams-Sonoma