Rhubarb and Custard Crumble Bars (Printable)

Tangy rhubarb meets creamy custard beneath a golden crumble topping. A delightful British springtime treat.

# Ingredient List:

→ Rhubarb Layer

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

→ Shortbread Base & Crumble

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

→ Custard Layer

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

# Directions:

01 - Preheat oven to 350°F. Line a 9-inch square baking pan with parchment paper, leaving an overhang on all sides for easy removal.
02 - In a saucepan, combine chopped rhubarb, sugar, lemon juice, and cornstarch. Cook over medium heat, stirring frequently, until rhubarb softens and the mixture thickens, approximately 8 to 10 minutes. Transfer to a bowl and allow to cool.
03 - In a large mixing bowl, combine flour, rolled oats, brown sugar, and salt. Using your fingertips or a pastry cutter, work the cold butter into the mixture until it resembles coarse breadcrumbs.
04 - Press two-thirds of the crumble mixture firmly and evenly into the bottom of the prepared baking pan to create a compact base layer. Reserve the remaining crumble for topping.
05 - Bake the base layer for 15 minutes until lightly golden. Remove from oven and allow to cool slightly before proceeding.
06 - Heat milk in a saucepan until steaming but not boiling. In a separate bowl, whisk together egg yolks, sugar, and cornstarch until smooth. Gradually pour the hot milk into the egg mixture while whisking continuously. Return combined mixture to the 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 the cooled rhubarb mixture evenly over the baked shortbread base. Pour the prepared custard layer over the rhubarb, spreading to cover completely.
08 - Sprinkle the reserved crumble mixture evenly and generously over the custard layer.
09 - Bake for 30 minutes until the crumble topping is golden brown and the custard layer is just set.
10 - Allow bars to cool completely in the pan. Once cooled, refrigerate for a minimum of 2 hours before removing from pan and cutting into 16 bars.

# Expert Tips:

01 -
  • The tangy rhubarb cuts through the richness of the custard in a way that feels balanced and bright.
  • You get three textures in one bite: creamy, fruity, and buttery crunch.
  • They slice cleanly and look impressive, but they come together without any fussy techniques.
  • Perfect for using up rhubarb when it's in season and you don't know what else to bake.
02 -
  • Don't skip chilling the bars, if you try to cut them warm, the custard will ooze out and you'll end up with a messy pile instead of neat squares.
  • Cold butter is absolutely essential for the crumble, if it's too soft, the mixture will turn greasy instead of forming those lovely crumbly bits.
  • Stir the custard constantly while it's thickening or you'll end up with scrambled eggs instead of smooth, creamy custard.
03 -
  • Freeze the butter for 10 minutes before you start if your kitchen is warm, it makes rubbing it into the flour so much easier.
  • Taste your rhubarb before cooking, if it's super tart, add an extra tablespoon of sugar to the compote so it's not too sour.
  • Let the custard cool for a few minutes before pouring it over the rhubarb, this prevents the layers from mixing together.
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