Instructions: Make the Short Crust Dough: In the bowl of a heavy-duty mixer fitted with the paddle attachment, mix flour, sugar, and salt on medium-low speed to combine. Add butter, and continue mixing until coarse crumbs form. Add egg yolk; mix just until dough comes together. Roll dough out, about 1/8-inch thick, between two layers of parchment paper. Chill until firm, about 1 hour. (

Makes about 1 1/2 pounds)

Heat oven to 350 degrees. Remove short crust dough from refrigerator. Remove parchment paper covering top, and invert onto a baking sheet. Press an 11-inch flan ring in center of short crust dough to cut out a circle. Keeping flan ring on baking sheet, trim excess dough from outside of ring, and reserve for another use. Prick circle of dough several times with a fork. Chill until firm, about 20 minutes.

Remove dough-lined flan ring from refrigerator. Bake until a light golden brown, 15 to 18 minutes. Cool completely on a wire rack before filling.

Combine creme fraiche, eggs, egg yolks, lemon zest, lemon juice, vanilla bean, and sugar in a medium-size heat-proof bowl. Place over a pot of simmering water. Cook, stirring occasionally until mixture thickens, about 20 minutes.

Remove from heat, and stir in softened gelatin sheets. Strain mixture through a fine mesh sieve set over a medium-size bowl. Cover surface of mixture with plastic wrap to prevent skin from forming. Set mixture in an ice bath to cool to 100 degrees.

Add butter, and using a handheld immersion blender, mix for 5 minutes. Pour into prebaked tart shell. Chill until mixture is firm, 2 to 3 hours.

Just before serving, sprinkle individual slices with a light, even layer of sugar. Caramelize the sugar to a golden brown, using a blow torch or placing under a broiler.

This recipe yields 10 servings.

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