# What You'll Need:
→ Tart Crust
01 - 1.5 cups all-purpose flour
02 - 7 tablespoons cold unsalted butter, cubed
03 - 3.5 tablespoons powdered sugar
04 - 1 large egg yolk
05 - 1 to 2 tablespoons cold water
06 - Pinch of salt
→ Custard Filling
07 - 5.25 ounces white chocolate, finely chopped
08 - 1 cup heavy cream
09 - 3.4 fluid ounces whole milk
10 - 3.4 fluid ounces elderflower cordial
11 - 3 large egg yolks
12 - 2.1 tablespoons granulated sugar
13 - 1 teaspoon vanilla extract
→ Rhubarb Topping
14 - 10.5 ounces rhubarb, trimmed and cut into 2-inch batons
15 - 4.2 tablespoons 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 chilled 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. Whisk egg yolks, sugar, and vanilla in a bowl 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 hot custard mixture; 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.