# What You'll Need:
→ Tart Crust
01 - 1.6 cups all-purpose flour
02 - 7 tablespoons cold unsalted butter, cubed
03 - 0.25 cup powdered sugar
04 - 1 large egg yolk
05 - 1 to 2 tablespoons cold water
06 - Pinch of salt
→ Custard Filling
07 - 5.3 ounces white chocolate, finely chopped
08 - 1 cup heavy cream
09 - 3.4 tablespoons whole milk
10 - 0.25 cup elderflower cordial
11 - 3 large egg yolks
12 - 2 tablespoons granulated sugar
13 - 1 teaspoon vanilla extract
→ Rhubarb Topping
14 - 10.6 ounces rhubarb, trimmed and cut into 2-inch batons
15 - 0.25 cup granulated sugar
16 - Zest of 1 lemon
17 - 2 tablespoons elderflower cordial
# Directions:
01 - In a food processor, pulse flour, butter, powdered sugar, and salt until mixture resembles breadcrumbs. Add egg yolk and 1 tablespoon cold water; pulse until dough begins to come together, adding more water if needed. Shape into a disk, wrap in plastic, and chill for 30 minutes.
02 - Roll out dough on a floured surface to fit a 9-inch tart tin. Press into tin, trim edges, and chill for 15 minutes. Preheat oven to 350°F. Line crust with parchment and baking beans; blind bake for 15 minutes. Remove beans and parchment, bake 5 to 7 minutes more until golden. Cool completely.
03 - In a saucepan, heat cream and milk until steaming but not boiling. In a bowl, whisk egg yolks, sugar, and vanilla until pale. Slowly pour hot cream mixture into yolks, whisking constantly. Return mixture to saucepan over low heat, stirring until slightly thickened and coats the back of a spoon. Remove from heat.
04 - Add white chocolate and elderflower cordial to the saucepan; stir until smooth. Pour custard into cooled tart shell. Chill in refrigerator for at least 1 hour until set.
05 - Preheat oven to 375°F. Arrange rhubarb batons in a single layer in a baking dish. Sprinkle with sugar, lemon zest, and drizzle with elderflower cordial. Cover with foil and roast for 15 minutes. Remove foil, roast 5 to 8 minutes more until tender but not falling apart. Cool completely.
06 - Arrange cooled rhubarb over set custard. Optionally, brush with a little extra elderflower cordial for shine. Chill until ready to serve.