Rhubarb and Custard Crumble Bars (Printable)

Tangy rhubarb meets creamy vanilla custard under a golden buttery crumble topping for an irresistible layered treat.

# 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 - 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

# How-To Steps:

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.
02 - Combine rhubarb, sugar, lemon juice, and cornstarch in a saucepan. Cook over medium heat, stirring frequently, until rhubarb softens and mixture thickens, approximately 8 to 10 minutes. Transfer to a bowl and cool.
03 - In a large bowl, combine flour, oats, brown sugar, and salt. Rub cold butter into the dry ingredients using your fingertips or a pastry cutter until the mixture resembles coarse breadcrumbs.
04 - Press two-thirds of the crumble mixture firmly and evenly across the bottom of the prepared pan. 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, sugar, and cornstarch until smooth. Slowly pour hot milk into egg mixture while whisking constantly. Return to saucepan and cook over medium heat, stirring continuously, until thickened, approximately 2 to 3 minutes. Remove from heat and stir in vanilla extract.
07 - Spread cooled rhubarb compote evenly over the baked base. Pour custard mixture over the rhubarb layer.
08 - Sprinkle reserved crumble mixture evenly across the custard layer.
09 - Bake for 30 minutes until the crumble is golden brown and the custard is just set.
10 - Cool completely in the pan, then refrigerate for at least 2 hours. Use parchment overhang to lift bars from pan and cut into 16 equal portions.

# Expert Hints:

01 -
  • Three textures in every bite: crumbly, creamy, and jammy all at once.
  • It uses up seasonal rhubarb in the most comforting way possible.
  • You can make it ahead and serve it cold, which makes hosting so much easier.
  • The custard layer is like a secret hug between the fruit and the crumble.
02 -
  • Do not skip chilling the bars, they need that time to set properly or they will fall apart when you cut them.
  • Use cold butter for the crumble, warm butter will make it greasy instead of crumbly.
  • Whisk the custard constantly while it thickens or you will end up with scrambled eggs instead of silky cream.
03 -
  • Line your pan with parchment in both directions so you can lift the bars out easily without any sticking.
  • Taste your rhubarb before cooking, if it is very tart, add an extra tablespoon of sugar to the fruit layer.
  • Make the custard right before you need it so it is still warm and spreadable when you pour it over the rhubarb.
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