Ingredients
2 tablespoons plus 1 1/2 teaspoons packed light-brown sugar
1 1/2 tablespoons unsalted butter
2 tablespoons light corn syrup
Pinch of salt
1/4 cup cake flour (not self-rising)
1 ounce hazelnuts (about 1/4 cup) toasted, skins rubbed off with a damp cloth, and finely ground, or 2 tablespoons hazelnut flour
1/4 cup plus 2 tablespoons cold water
1 teaspoon unflavored gelatin
1 cup granulated sugar
2 tablespoons light corn syrup
2 1/2 tablespoons unsalted butter, room temperature, cut into small pieces
1 3/4 cups heavy cream
1/2 cup creme fraiche
Pinch of salt
3 oranges, preferably Cara Cara
2 blood oranges
1 red or pink grapefruit
2 tangerines
1 Meyer lemon
Preparation
Make the cookies: Preheat oven to 350 degrees. Heat sugar, butter, corn syrup, and salt in a saucepan over medium heat, stirring until butter has melted and sugar has dissolved. Stir in flour and ground hazelnuts. Drop teaspoons of batter, spaced 2 inches apart, onto a baking sheet lined with a nonstick baking mat. Bake until golden, 10 to 12 minutes. Let cool. (Cookies can be stored in an airtight container for up to 2 days.)
Make the mousse: Place 2 tablespoons cold water in a bowl, and sprinkle with gelatin. Let stand for 5 minutes.
Bring sugar, corn syrup, and remaining 1/4 cup water to a boil in a saucepan over medium heat, stirring to dissolve sugar. Wash down sides of pan with a wet pastry brush to prevent sugar crystals from forming. Cook, swirling gently once mixture begins to color, until dark amber, 12 to 13 minutes.
Remove from heat. Carefully add butter, a few pieces at a time, whisking after each addition until butter melts (caramel will bubble). Add 1/4 cup each cream and creme fraiche. Add salt, and whisk until smooth. Transfer to a bowl. Add gelatin mixture, and stir until combined. Let cool completely, stirring occasionally.
In a bowl, whisk remaining 1 1/2 cups cream and 1/4 cup creme fraiche until stiff peaks form. Gently fold into caramel. Cover mousse, and refrigerate for 10 minutes (or overnight).
Assemble parfaits: Cut peel and pith from citrus. Slice fruit along membranes to release segments.
Layer segments and mousse in 6 serving glasses, beginning and ending with segments. Refrigerate, covered, until mousse is set, at least 1 hour (or overnight). Serve with lace cookies.
