famed pastry chef Pierre Hermé. I combine everything but the butter in a stainless steel bowl and cook it over simmering water, whisking constantly, as one would for a sabayon. When it’s thickened to the consistency of thin mayonnaise, I remove it from the heat and whisk in the softened butter and citrus zest. Hermé actually puts
the custard in a blender and then adds the butter. Either way, the result is a very creamy curd that makes an ideal filling for tarts or, in this case, crunchy, green-hued macarons. As an optional garnish for the macarons, I brushed the tops of some with a little watered down gel color and let it dry.
Makes about 24 filled macarons
2 1/3 cups (300 g) confectioners’ sugar
1 ¼ cups (160 g) almond flour
4 large egg whites, at room temperature
¼ teaspoon cream of tartar
1/3 cup (66 g) granulated sugar
½ teaspoon vanilla extract
Leaf green gel food coloring
Key Lime Curd Filling:
2 large eggs
2 large egg yolks
1/3 cup (66 g) granulated sugar
1/3 cup (80 g) freshly squeezed strained Key or Persian lime juice
Pinch of salt
5 tablespoons (70 g) unsalted butter, cut into tablespoons and softened
1 tablespoon (6 g) finely grated lime zest
Make the filling:
1. Fill a medium saucepan one-third of the way with water and bring the water to a simmer. In a medium bowl, whisk together the eggs, egg yolks, sugar, lime juice and salt until blended. Place the bowl over the saucepan and heat the mixture, whisking constantly, until it is uniformly pale and thickened to the consistency of thin mayonnaise, 5 to 8 minutes. Remove the bowl from over the saucepan of water and whisk in the softened butter 1 tablespoon at a time, whisking until each piece is incorporated before adding the next. Whisk in the lime zest. Cover the surface of the filling with a piece of plastic wrap and refrigerate the filling for at least 2 hours before using.
Make the macarons:
2. Line two baking sheets with silicone baking mats or parchment paper.
3. Place the confectioners’ sugar and almond flour in the bowl of a food processor and process for about 10 seconds, until well combined. Pass the mixture through a medium-mesh sieve into a bowl and set aside.
4. In the bowl of a stand mixer fitted with the whisk attachment, beat the egg whites at medium speed until frothy. Add the cream of tartar and beat the mixture until the whites turn opaque and begin to form very soft peaks. Gradually add the sugar while gradually increasing the speed to high, and beat until stiff peaks form. Remove the bowl from the stand and gently fold in the vanilla extract and food coloring, adding enough color to turn the whites a vibrant green (the color will fade slightly during baking). Gently fold in half of the almond mixture until almost combined. Add the remaining half and gently fold until combined. Continue to fold the mixture just until the batter drips down from the spatula in a continuous lava-like flow. This can take anywhere from 20 to 40 strokes, depending on how strong your arm is. You don’t want the batter to be too thick (the macaron tops won’t be smooth) or too thin (the macarons will spread too much and won’t puff up). This is called macaronnage, and is probably the most important step in making macarons.
5. Fit a disposable plastic pastry bag with a plain tip (Ateco #4) and stand it up in a tall glass. Spoon about half of the batter into the bag (cover the surface of the remaining batter with plastic wrap and set aside). Pipe the batter into ¾-inch round on the prepared sheets, spacing them about an inch apart. Hold the baking sheet about 5 or 6 inches from a work surface and let it drop onto the surface about 4 or 5 times; this will eliminate many of the air bubbles in the macarons. Let the macarons stand at room temperature for 20 to 30 minutes before baking (this will aid in the formation of the pied (foot), the ruffled part at the base of the macaron.
6. Position a rack in the lower third of the oven and preheat the oven to 350°F. Bake the macarons, one sheet at a time, for 12 to 14 minutes, until they have puffed up nicely. Cool them on the sheet set on a wire rack before removing. Repeat with the remaining batter.
Fill the macarons:
7. Place the filling in a pastry bag (with a medium plain tip or no tip at all) and pipe a dollop onto the underside of half the macarons. Top with the remaining macarons. Place the filled macarons in an airtight container and refrigerate for at least a day before serving (or eating).