Rhubarb and Custard Crumble Bars (Printable)

Layered bars with tangy rhubarb, vanilla custard, and golden buttery crumble topping. A British springtime delight.

# What You'll Need:

→ Rhubarb Layer

01 - 14 ounces fresh rhubarb, trimmed and chopped
02 - 5.3 ounces granulated sugar
03 - 1 tablespoon fresh lemon juice
04 - 1 tablespoon cornstarch

→ Shortbread Base and Crumble

05 - 8.8 ounces all-purpose flour
06 - 3.5 ounces rolled oats
07 - 5.3 ounces unsalted butter, cold and cubed
08 - 3.5 ounces light brown sugar
09 - 0.5 teaspoon salt

→ Custard Layer

10 - 10 fluid ounces whole milk
11 - 2 large egg yolks
12 - 2.1 ounces granulated sugar
13 - 2 tablespoons cornstarch
14 - 1 teaspoon vanilla extract

# Method:

01 - Preheat oven to 350°F. Line a 9-inch square baking pan with parchment paper, allowing paper to extend beyond edges for easy removal.
02 - Combine rhubarb, sugar, lemon juice, and cornstarch in a saucepan. Cook over medium heat, stirring frequently, until rhubarb softens and mixture thickens, approximately 8 to 10 minutes. Transfer to a bowl and allow to cool.
03 - In a large mixing bowl, combine flour, oats, brown sugar, and salt. Using your fingertips or a pastry cutter, work in the cold butter until mixture resembles coarse breadcrumbs.
04 - Press two-thirds of the crumble mixture firmly and evenly into the bottom of the prepared pan, creating a uniform base. Reserve remaining crumble for topping.
05 - Bake base for 15 minutes until lightly golden. Remove from oven and allow to cool slightly.
06 - Heat milk in a saucepan until steaming but not boiling. In a separate bowl, whisk egg yolks, sugar, and cornstarch until smooth. Slowly pour hot milk into egg mixture while whisking continuously. Return combined mixture to saucepan and cook over medium heat, stirring constantly, until thickened, approximately 2 to 3 minutes. Remove from heat and stir in vanilla extract.
07 - Spread cooked rhubarb evenly over the baked shortbread base. Pour prepared custard layer evenly over rhubarb.
08 - Distribute reserved crumble mixture evenly across the custard layer.
09 - Bake for 30 minutes until crumble turns golden and custard sets completely.
10 - Cool completely in pan, then refrigerate for at least 2 hours before removing and cutting into 16 bars.

# Expert Advice:

01 -
  • Three layers mean three textures in every bite, so nobody gets bored halfway through.
  • The rhubarb stays tart enough to keep things interesting, unlike recipes that smother it in sugar.
  • You can make these ahead and they actually taste better after chilling overnight.
02 -
  • Rushing the cooling step is the only real way to ruin these bars, so patience here actually determines whether you get clean slices or a dessert that needs to be scooped with a spoon.
  • The custard should thicken while still on the heat, and if it seems too thin, you haven't cooked it long enough, but if it breaks or curdles, your milk was probably too hot when you added it.
03 -
  • If your rhubarb is particularly stringy, peel off the toughest fibres with a vegetable peeler before chopping, and your teeth will thank you.
  • Adding a small handful of raspberries to the rhubarb layer introduces subtle sweetness and complexity without overpowering the tart character.
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