Rhubarb and Custard Crumble Bars (Printable)

Tangy rhubarb and creamy custard topped with golden buttery crumble. A delightful springtime dessert.

# What You'll Need:

→ 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 - 1/2 teaspoon salt

→ Custard Layer

10 - 10.1 fl oz whole milk
11 - 2 large egg yolks
12 - 2.1 oz granulated sugar
13 - 2 tablespoons cornstarch
14 - 1 teaspoon vanilla extract

# How to Make It:

01 - Preheat oven to 350°F. Line a 9-inch square baking pan with parchment paper, leaving an overhang for easy removal.
02 - In a saucepan, combine rhubarb, sugar, lemon juice, and cornstarch. Cook over medium heat, stirring often, until rhubarb softens and mixture thickens, approximately 8 to 10 minutes. Set aside to cool.
03 - In a large bowl, mix flour, oats, brown sugar, and salt. Rub in the cold butter with your fingers or a pastry cutter until the mixture resembles coarse crumbs.
04 - Press two-thirds of the crumble mixture firmly into the bottom of the prepared pan to form an even base. Reserve the remaining crumble for the topping. Bake the base for 15 minutes until lightly golden. Remove from oven and let cool slightly.
05 - In a saucepan, heat the milk until steaming but not boiling. In a bowl, whisk egg yolks, sugar, and cornstarch until smooth. Gradually pour in the hot milk, whisking constantly. Return mixture to the pan and cook over medium heat, stirring, until thickened, approximately 2 to 3 minutes. Remove from heat and stir in vanilla extract.
06 - Spread the cooked rhubarb evenly over the baked base. Pour the custard layer over the rhubarb.
07 - Sprinkle the reserved crumble mixture evenly over the top.
08 - Bake for 30 minutes, or until the crumble is golden and the custard is just set. Cool completely in the pan, then chill for at least 2 hours before lifting out and cutting into 16 bars.

# Expert Hints:

01 -
  • The tangy rhubarb cuts through the creamy custard in a way that feels bright and balanced, not too sweet.
  • You get three textures in every bite: crisp crumble, silky custard, and soft fruit.
  • They slice cleanly once chilled, so you can pack them for picnics or stack them on a plate without a mess.
  • The oat crumble adds a nutty depth that plain shortbread just cant match.
02 -
  • Don't skip chilling the bars, warm custard will smear and the layers won't hold their shape when you cut.
  • If your rhubarb is very tart, add an extra tablespoon of sugar to the fruit mixture so it doesn't pucker your mouth.
  • Make sure the butter is truly cold when you make the crumble, or it will turn greasy instead of crumbly.
03 -
  • Line your pan with enough parchment overhang to lift the whole block out in one piece, it makes slicing so much easier.
  • Whisk the custard constantly once the milk goes in, even 30 seconds of distraction can lead to lumps.
  • Chill the bars overnight if you have time, the flavors meld together and the texture becomes even more satisfying.
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