01 -
Cream the butter and powdered sugar using a stand mixer fitted with a paddle attachment on low speed.
02 -
Add the egg and mix briefly, then fold in all-purpose flour, cake flour, kosher salt, and chopped pecans until just combined.
03 -
Shape the dough into a flat disk and refrigerate for 30 minutes if the dough is sticky.
04 -
Roll the chilled dough onto a floured surface into a 12-inch circle. Transfer to a 9.5-inch tart pan, pressing firmly into the edges and trimming excess.
05 -
Freeze the tart shell for 30 to 60 minutes. Preheat oven to 350°F. Line the crust with parchment paper and pie weights. Bake for 24 to 28 minutes, removing the weights for the final 5 minutes. Allow the crust to cool completely.
06 -
In a large saucepan over medium heat, melt the butter and granulated sugar, stirring continuously until the mixture reaches an amber color and smooth texture (5 to 7 minutes).
07 -
In a separate small saucepan, heat the heavy cream to a simmer and keep warm. Remove caramel from heat and slowly whisk in the warm cream until combined. Stir in fleur de sel and cinnamon. Cool the caramel for 15 minutes, then pour it into the cooled tart crust. Refrigerate for 1 hour.
08 -
Sprinkle gelatin over water in a small bowl and let it bloom for 5 minutes.
09 -
Heat 1/4 cup heavy cream, stir in the bloomed gelatin until dissolved. Pour hot cream over chopped white chocolate and stir until smooth. Allow to cool.
10 -
Whip the remaining 3/4 cup heavy cream with granulated sugar to soft peaks. Gently fold whipped cream into the cooled white chocolate mixture.
11 -
Pour the mousse over the caramel layer in the tart. Refrigerate for 2 hours before serving.