Rhubarb and Custard Crumble Bars (Printable)

Tangy rhubarb meets creamy custard under a golden buttery crumble. A delightful British springtime treat.

# What You'll Need:

→ Rhubarb Layer

01 - Fresh rhubarb, trimmed and chopped - 14 oz
02 - Granulated sugar - 2.6 oz
03 - Fresh lemon juice - 1 tablespoon
04 - Cornstarch - 1 tablespoon

→ Shortbread Base & Crumble

05 - All-purpose flour - 8.8 oz
06 - Rolled oats - 3.5 oz
07 - Unsalted butter, cold and cubed - 5.3 oz
08 - Light brown sugar - 3.5 oz
09 - Salt - 1/2 teaspoon

→ Custard Layer

10 - Whole milk - 10.1 fl oz
11 - Large egg yolks - 2
12 - Granulated sugar - 2.1 oz
13 - Cornstarch - 2 tablespoons
14 - Pure vanilla extract - 1 teaspoon

# 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, combine 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 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, 2 to 3 minutes. Remove from heat and stir in vanilla.
06 - Spread the cooked rhubarb evenly over the baked base. Pour the custard layer over the rhubarb. Sprinkle the reserved crumble mixture evenly over the top.
07 - 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 Advice:

01 -
  • The custard layer adds a creamy surprise that balances the tartness of rhubarb beautifully.
  • You get three textures in one bite: crumbly oat topping, smooth custard, and jammy fruit.
  • They slice cleanly and hold up well, making them ideal for packing or sharing at picnics.
  • The recipe uses simple pantry staples and fresh rhubarb without any fussy techniques.
02 -
  • Cold butter is essential for a crumbly topping, if it's too soft, the mixture will clump and turn greasy instead of crisp.
  • Whisk the custard constantly while it heats or it will form lumps and stick to the bottom of the pan.
  • Don't skip the chilling step, warm bars will fall apart when you try to slice them, and the custard won't hold its shape.
  • If your rhubarb is very tart, taste the cooked filling and add an extra tablespoon of sugar if needed before spreading it on the base.
03 -
  • Press the base firmly into the pan so it doesn't crumble apart when you slice, using the bottom of a measuring cup helps create an even, compact layer.
  • Let the rhubarb cool completely before spreading it on the base, or the heat will soften the shortbread and make it soggy.
  • If the crumble topping browns too quickly, tent the pan loosely with foil for the last ten minutes of baking.
  • Use a sharp knife wiped clean between cuts for the neatest bars, and lift them out of the pan before slicing for easier handling.
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