Rhubarb and Custard Crumble Bars (Printable Version)

Fruity bars with tangy rhubarb, creamy custard filling, and buttery crumble topping. 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 and 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 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 two sides for easy removal after baking.
02 - Combine rhubarb, sugar, lemon juice, and cornstarch in a saucepan over medium heat. Stir frequently until rhubarb softens and mixture thickens, approximately 8 to 10 minutes. Transfer to a bowl and allow to cool completely.
03 - In a large bowl, combine flour, oats, brown sugar, and salt. Using your fingertips or a pastry cutter, rub in the cold butter until the mixture resembles coarse breadcrumbs. Reserve one-third of the mixture for topping.
04 - Press two-thirds of the crumble mixture firmly and evenly into the bottom of the prepared pan. Bake for 15 minutes until lightly golden. Remove from oven and allow to cool slightly before adding subsequent layers.
05 - Heat milk in a saucepan until steam rises but mixture does not boil. In a separate bowl, whisk together 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.
06 - Spread cooled rhubarb mixture evenly over the baked base layer. Pour custard layer over the rhubarb, spreading to cover uniformly.
07 - Sprinkle reserved crumble mixture evenly across the custard layer.
08 - Bake for 30 minutes until crumble topping is golden brown and custard is set. Cool completely in pan, then refrigerate for at least 2 hours. Lift out using parchment overhang and cut into 16 bars.

# Additional Tips::

01 -
  • The tangy rhubarb cuts through the sweetness in a way that feels bright and alive, not cloying.
  • You get three textures in one bite: creamy custard, soft fruit, and that crumbly buttery top.
  • It slices cleanly into bars, so you can serve it without the fuss of plating individual portions.
  • The whole thing comes together in about an hour, and most of that time is hands off baking.
02 -
  • Cold butter is essential for a crumbly topping, if it softens too much, pop the bowl in the fridge for ten minutes before mixing.
  • Don't skip the chilling step, warm custard bars will smear and collapse when you try to cut them.
  • Stir the custard constantly once it goes back on the heat or you'll end up with lumps that no amount of whisking will smooth out.
03 -
  • Line the pan with enough parchment overhang to lift the whole slab out in one piece, it makes cutting so much cleaner.
  • Let the baked base cool for a few minutes before adding the rhubarb layer so the heat doesn't make the fruit weep and turn watery.
  • If the crumble topping browns too fast, tent the pan loosely with foil for the last ten minutes of baking.
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