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1
Line 2 baking sheets with parchment paper.
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2
Grind 1 cup of the confectioners' sugar, the hazelnuts, and cocoa in a food processor until powdery, about 3 minutes.
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3
Sift mixture through a medium mesh strainer onto a piece of parchment paper, then discard any large pieces of nuts that didn't come through the strainer.
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4
With an electric mixer, beat the egg whites and salt until they hold firm but not dry peaks, about 2 minutes.
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5
Gradually add the remaining 1 cup confectioners' sugar, a tablespoon at a time, scraping down the sides of the bowl as needed; this can take up to 3 minutes.
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6
Beat for an extra 30 seconds until the peaks are firm and shiny but still not dry.
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7
Fold the nut mixture gently into the egg whites with a large rubber spatula.
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8
Transfer mixture into a large piping bag fitted with a 1/2-inch plain piping tip.
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9
Pipe 32 2-inch by about 1/3-inch thick rounds, evenly spaced, on each of the prepared pans.
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10
Set aside to air dry for 30 minutes before baking.
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11
Meanwhile make the filling: Put chocolate in a medium heatproof bowl.
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12
In a small saucepan, bring cream, with espresso powder mixed in, to a boil.
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13
Pour cream over chocolate and shake bowl gently so cream settles around the chocolate.
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14
Set mixture aside until the chocolate is soft, about 5 minutes.
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15
Whisk gently until smooth, taking care not to incorporate too many air bubbles.
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16
Cool at room temperature until set up.
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17
Preheat oven to 325 degrees F.
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18
Bake macaroons until set and puffed, about 18 to 20 minutes.
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19
Take care not to overcook the macaroons or they'll crack.
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20
Cool cookies for 5 minutes then gently peel from paper.
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21
Let cool completely.
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22
Spread 1 teaspoon of mocha filling on a cookie and sandwich 2 cookies together.
