Rhubarb White Chocolate Elderflower Tart

My neighbor brought me a bundle of rhubarb stalks one April morning, their leaves still dewy. I had white chocolate left from Easter and a bottle of elderflower cordial I'd been hoarding. The tart came together almost by accident, but when I sliced into it that evening, the custard had set like silk and the rhubarb glowed pink against the cream. It's been my spring celebration dessert ever since.

I served this at a garden party once, and three people asked for the recipe before dessert plates were cleared. One guest thought I'd ordered it from a patisserie. The tartness of the rhubarb cuts through the richness in a way that feels balanced, not cloying. Even people who claim they don't like white chocolate ask for seconds.

Ingredients

• All-purpose flour: Forms the base of a tender, buttery crust that won't crumble when you slice it.
• Cold unsalted butter: Keeps the pastry flaky; cube it small and work quickly so it doesn't melt.
• Powdered sugar: Sweetens the crust gently and helps it brown evenly without graininess.
• Egg yolk: Binds the dough and adds richness; save the white for meringue another day.
• Cold water: Use just enough to bring the dough together; too much makes it tough.
• White chocolate: Choose a good quality brand with real cocoa butter for a custard that sets properly.
• Heavy cream: Creates the luscious body of the custard; don't substitute with anything lighter.
• Whole milk: Thins the custard just enough so it pours smoothly into the shell.
• Elderflower cordial: Adds a delicate, honey-like floral note that makes this tart unforgettable.
• Egg yolks: Thicken the custard and give it a silky, pale yellow hue.
• Granulated sugar: Balances the tang of rhubarb and sweetens the custard base.
• Vanilla extract: A quiet background note that deepens the flavor without announcing itself.
• Rhubarb: Look for firm, bright stalks; avoid any that feel soft or have brown spots.
• Lemon zest: Brightens the roasted rhubarb and keeps it from tasting flat.

Instructions

Prepare the Tart Crust:

Pulse the flour, cold butter cubes, powdered sugar, and salt in a food processor until the mixture looks like coarse breadcrumbs. Add the egg yolk and a tablespoon of cold water, pulsing just until the dough starts to clump together; if it's still too dry, add another tablespoon of water.

Chill and Roll:

Shape the dough into a flat disk, wrap it tightly in plastic, and refrigerate for 30 minutes. Roll it out on a floured surface until it's large enough to line your 23-cm tart tin, then press it gently into the corners, trim the edges, and chill again for 15 minutes.

Blind Bake:

Preheat your oven to 180°C (350°F), line the chilled crust with parchment paper, fill it with baking beans, and bake for 15 minutes. Remove the beans and parchment, then bake for another 5 to 7 minutes until the crust is golden and crisp; let it cool completely.

Make the Custard Filling:

Heat the cream and milk in a saucepan until steaming, then whisk the egg yolks, sugar, and vanilla in a bowl until pale and smooth. Slowly pour the hot cream into the yolks while whisking constantly, then return the mixture to the saucepan and stir over low heat until it thickens enough to coat the back of a spoon.

Finish the Custard:

Remove the custard from heat, add the chopped white chocolate and elderflower cordial, and stir until the chocolate melts and the mixture is glossy. Pour it into the cooled tart shell and refrigerate for at least an hour until fully set.

Roast the Rhubarb:

Preheat your oven to 190°C (375°F), arrange the rhubarb batons in a single layer in a baking dish, sprinkle with sugar and lemon zest, and drizzle with elderflower cordial. Cover with foil and roast for 15 minutes, then uncover and roast for another 5 to 8 minutes until tender but still holding its shape; cool completely before using.

Assemble the Tart:

Arrange the cooled rhubarb pieces over the set custard in any pattern you like. For extra shine, brush the rhubarb lightly with a bit more elderflower cordial, then chill until you're ready to serve.

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The first time I brought this to a dinner party, someone called it "the prettiest dessert I've ever made." I blushed, but secretly I agreed. There's something about the pale custard and the ruby rhubarb that feels like spring captured on a plate. It's become the dessert I make when I want to show someone I care.

How to Know When the Custard Is Ready

The custard should coat the back of a wooden spoon and hold a clear line when you drag your finger through it. It will thicken more as it cools, so don't wait for it to become pudding-thick on the stove. If you're nervous, use a thermometer and pull it off the heat at 80°C (176°F). The white chocolate will finish the thickening as it melts in.

Choosing and Preparing Rhubarb

Look for stalks that are firm and brightly colored, either pink or red. Trim off the leaves completely, as they're toxic, and wash the stalks well. Cut them into even pieces so they roast at the same rate. If your rhubarb is very thick, halve the stalks lengthwise first. The goal is pieces that soften but don't collapse into mush.

Make-Ahead and Serving Tips

You can bake the crust a day ahead and store it in an airtight container. The custard can be made and poured into the shell the night before, then covered and chilled. Roast the rhubarb in the morning and assemble the tart a few hours before serving. The flavors deepen as everything sits together, and the tart slices cleanest when fully chilled.

• Sprinkle toasted pistachios or slivered almonds over the top for crunch and color.
• Serve with a small dollop of lightly whipped cream or crème fraîche if you want extra richness.
• Pair it with a glass of chilled Moscato, elderflower spritz, or even a floral white tea.

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This tart has a way of making any occasion feel special, even if it's just a quiet Sunday with tea. Slice it cold, let the flavors unfold, and watch people go quiet with that first bite.

Recipe FAQs

→ Can I make this tart ahead of time?

Yes, this is an excellent make-ahead dessert. Prepare the tart shell and custard up to 2 days in advance, storing them separately in the refrigerator. Roast the rhubarb the day before and assemble just before serving for the best presentation.

→ What can I substitute for elderflower cordial?

If elderflower cordial is unavailable, try using a light floral honey mixed with a splash of lemon juice, or substitute with orange blossom water diluted with simple syrup. The flavor profile will change slightly but remain delicious.

→ How do I prevent the tart crust from becoming soggy?

Blind baking the crust until fully golden is essential. Ensure it cools completely before adding the custard. For extra protection, you can brush the cooled crust with a thin layer of melted white chocolate before filling.

→ Can I use frozen rhubarb instead of fresh?

Fresh rhubarb works best as it holds its shape better during roasting. If using frozen, thaw completely and pat very dry with paper towels before roasting, and reduce the roasting time slightly to prevent mushiness.

→ What type of white chocolate works best?

Use high-quality white chocolate with at least 30% cocoa butter for the smoothest, most flavorful custard. Avoid white baking chips, as they contain stabilizers that prevent proper melting and may result in a grainy texture.

→ How long will this tart keep in the refrigerator?

The assembled tart will keep for up to 2 days when covered and refrigerated. However, the rhubarb may release some moisture over time, so it's best enjoyed within 24 hours of assembly for optimal texture and presentation.