Rhubarb and Custard Crumble Bars (Printable)

Buttery bars with tangy rhubarb, creamy vanilla custard, and golden crumble topping—ideal for afternoon tea.

# What You Need:

→ Rhubarb Layer

01 - Fresh rhubarb, trimmed and chopped - 14 oz
02 - Granulated sugar - 2.6 oz
03 - 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 - Vanilla extract - 1 teaspoon

# How-To Steps:

01 - Preheat oven to 350°F. Line a 9-inch square baking pan with parchment paper, leaving overhang for easy removal.
02 - In a saucepan, combine chopped rhubarb, granulated sugar, lemon juice, and cornstarch. Cook over medium heat, stirring frequently, until rhubarb softens and mixture thickens, approximately 8-10 minutes. Set aside to cool.
03 - In a large bowl, mix flour, rolled oats, brown sugar, and salt. Rub in cold butter cubes with your fingers or pastry cutter until mixture resembles coarse breadcrumbs.
04 - Press two-thirds of the crumble mixture firmly into the bottom of the prepared pan to form an even base. Reserve remaining crumble for topping.
05 - Bake the 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, granulated sugar, and cornstarch until smooth. Gradually pour hot milk into egg mixture while whisking constantly. Return combined mixture to saucepan and cook over medium heat, stirring continuously, until thickened, approximately 2-3 minutes. Remove from heat and stir in vanilla extract.
07 - Spread cooled rhubarb mixture evenly over the baked base. Pour prepared custard layer evenly over the rhubarb.
08 - Sprinkle reserved crumble mixture evenly over the custard layer.
09 - Bake for 30 minutes, or until the crumble topping is golden and the custard is just set.
10 - Cool completely in the pan, then refrigerate for at least 2 hours before lifting out and cutting into 16 bars.

# Expert Suggestions:

01 -
  • The custard layer stays creamy even after chilling, like biting into a soft cloud between tartness and crunch.
  • You get three textures in one bar: buttery crumble, silky custard, and jammy fruit that never turns soggy.
02 -
  • Don't skip chilling the bars, they need that time for the custard to firm up or they'll fall apart when you cut them.
  • If your rhubarb is very tart, taste the cooked filling and add a tablespoon more sugar if needed before spreading it on the base.
03 -
  • Press the base firmly into the pan, a loose base will crumble when you try to cut the bars and make a mess of your pretty layers.
  • Whisk the custard constantly while it cooks, any pause and you risk scrambled eggs instead of silky cream.
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