For the cookies:
6 oz. slivered or blanched almonds
1½ oz. chopped hazelnuts
10 oz. confectioners’ sugar
3 large egg whites
1½ tsp. cream of tartar
For the filling:
¾ cup (12 tbsp.) unsalted butter, at room temperature
6 tbsp. Nutella
¾ cup confectioners’ sugar, sifted
Pinch of coarse salt
step 1: Show Images
Line two baking sheets with silicone baking mats or parchment paper. Have a pastry bag fitted with a large round tip ready (I use Ateco #809). In the bowl of a food processor, combine the almonds and hazelnuts. Pulse until mostly well ground. Add the confectioners’ sugar to the bowl and continue to process in brief pulses until the nuts are finely ground and the mixture is even. Set aside.
step 2: Show Images
In the bowl of a stand mixer fitted with the whisk attachment, combine the egg whites and cream of tartar. Whip on medium-high speed until stiff, glossy peaks form, about 3-4 minutes. Add about one third of the ground nut mixture to the bowl with the egg whites and fold in gently with a spatula. Fold in the remaining nut mixture in two additions, just until the ingredients are combined and no lumps or streaks remain. The batter will be fairly thick. Transfer the mixture to the pastry bag. Pipe 1-inch circles, about ½-inch thick, onto the prepared baking sheets spacing them about 1 inch apart. (They will spread slightly after piping but don’t worry.) Allow the cookies to rest at room temperature uncovered for 2 hours. (This step helps the cookies develop the delicate exterior crust and “foot” on the bottom.)
step 3: Show Images
Preheat the oven to 300˚ F and set oven racks in the the lower half of the oven. Bake, rotating the pans halfway through baking, until the macarons appear set but are not browned, about 12-14 minutes. Let cool. (To ensure adequate drying of the cookies, I like to shut off the oven at the end of baking, prop the door open slightly with a wooden spoon, and let the shells cool slowly in the oven.) Once the cookies are cool, carefully remove them from the baking mats and transfer to a wire rack, matching them up in pairs by size.
step 4: Show Images
To make the filling, combine the butter and nutella in the bowl of an electric mixer fitted with the paddle attachment. Beat on medium-high speed until smooth, about 1-2 minutes. Blend in the confectioners’ sugar and salt, then beat on high speed until light and fluffy, 2-3 minutes more.
step 5: Show Images
Pipe a small dollop of the nutella mixture onto the flat side of one cookie of each pair. Sandwich together with the remaining cookie, pushing the filling to the edges. Store in an airtight container.