# What You'll Need:
→ Tart Crust
01 - 1.75 cups all-purpose flour
02 - 7 tablespoons cold unsalted butter, cubed
03 - 0.33 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 - 1.06 cups heavy cream
09 - 0.21 cup 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
# How To Make It:
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 and trim edges; 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, then bake 5 to 7 minutes more until golden. Cool completely.
03 - Heat cream and milk in a saucepan until steaming but not boiling. Whisk egg yolks, sugar, and vanilla in a bowl until pale. Slowly pour hot cream mixture into yolks while whisking constantly. Return mixture to saucepan over low heat, stirring until slightly thickened and coating the back of a spoon. Remove from heat and stir in white chocolate and elderflower cordial until smooth.
04 - Pour custard into cooled tart shell and chill in refrigerator for at least 1 hour until completely 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 and roast 5 to 8 minutes more until tender but not falling apart. Cool completely.
06 - Arrange cooled rhubarb over set custard. Optionally brush with additional elderflower cordial for shine. Chill until ready to serve.