Ingredients
- 6 large egg whites
- 1-1/2 cups hazelnuts, toasted
- 2-1/2 cups confectioners’ sugar
- Dash salt
- 1/2 cup superfine sugar
- coffee buttercream:
- 1 cup sugar
- 6 tablespoons water
- 6 large egg yolks
- 4 teaspoons instant espresso powder
- 1 teaspoon vanilla extract
- 1-1/2 cups butter, softened
- 6 tablespoons confectioners’ sugar
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- Place egg whites in a small bowl; let stand at room temperature for 30 minutes.
- Preheat oven to 350°. Place hazelnuts and confectioners’ sugar in a food processor; pulse until nuts are finely ground.
- Add salt to egg whites; beat on medium speed until soft peaks form. Gradually add superfine sugar, 1 tablespoon at a time, beating on high until stiff peaks form. Fold in hazelnut mixture.
- Transfer mixture to a pastry bag fitted with a round tip. Pipe 1-in.-diameter cookies 2 in. apart onto parchment-lined baking sheets. Bake until lightly browned and firm to the touch, 9-12 minutes. Transfer cookies on the parchment to wire racks; cool completely.
- For the buttercream, in a heavy saucepan, combine sugar and water. Bring to a boil; cook over medium-high heat until sugar is dissolved. Remove from heat. In a small bowl, whisk a small amount of hot syrup into egg yolks; return all to pan, whisking constantly. Cook until thickened, 2-3 minutes, stirring constantly; remove from heat. Stir in espresso powder and vanilla; cool completely.
- In a stand mixer with the whisk attachment, beat butter until creamy. Gradually beat in cooled syrup. Beat in confectioners’ sugar until fluffy. Refrigerate until mixture firms to a spreading consistency, about 10 minutes.
- Spread about 1-1/2 tsp buttercream onto the bottoms of half the cookies; top with remaining cookies. Store in airtight containers in the refrigerator.
