Rhubarb and Custard Crumble Bars (Printable Version)

Tangy rhubarb and vanilla custard layered between buttery crumble. A delightful British springtime dessert.

# What You 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 - 10.1 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, allowing overhang on 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. Set aside to cool.
03 - Mix flour, oats, brown sugar, and salt in a large bowl. 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 into the bottom of the prepared pan to create an even, compact 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, sugar, and cornstarch until smooth. Gradually pour hot milk into egg mixture while whisking constantly. Return combined mixture to the saucepan and cook over medium heat, stirring continuously, until thickened, 2 to 3 minutes. Remove from heat and stir in vanilla extract.
07 - Spread cooled rhubarb filling evenly over the baked shortbread base. Pour custard layer carefully over the rhubarb layer.
08 - Sprinkle reserved crumble mixture evenly across the top of the custard layer.
09 - Bake for 30 minutes, or until the crumble topping is golden brown and custard is set but still slightly soft in the center.
10 - Allow bars to cool completely in the pan at room temperature. Refrigerate for a minimum of 2 hours before removing from pan and cutting into 16 equal bars.

# Expert Advice:

01 -
  • Three textures in every bite: buttery crumble, silky custard, and tart fruit that wakes up your tongue.
  • They slice clean after chilling, so you can pack them for picnics without the mess of a spoon dessert.
  • The rhubarb sharpness cuts through the sweetness in a way that feels more grown up than most bar cookies.
  • You can make them a day ahead and they actually taste better after a night in the fridge.
02 -
  • Don't skip chilling the bars, warm custard will smear everywhere and you'll end up with a beautiful mess instead of neat squares.
  • If your rhubarb is very thick, split the stalks lengthwise before chopping so they cook at the same rate as the thinner pieces.
  • Press the base firmly or it will crumble apart when you cut the bars, I learned this after my first batch fell into rubble.
  • Whisk the custard constantly once the milk goes in or you'll get scrambled eggs instead of silky cream.
03 -
  • Use a sharp knife dipped in hot water and wiped dry between cuts for the cleanest edges on your bars.
  • If the custard seems too thick as it cools, whisk in a tablespoon of milk to loosen it before pouring over the rhubarb.
  • Make extra crumble topping and freeze it, then you can sprinkle it over fruit crisps or morning yogurt without making a whole new batch.
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