Rhubarb and Custard Crumble Bars (Print View)

Layered bars with tangy rhubarb, vanilla custard, and buttery crumble topping. Ideal for springtime or afternoon tea.

# Components:

→ Rhubarb Layer

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

→ 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 tsp

→ Custard Layer

10 - Whole milk - 10 fl oz
11 - Large egg yolks - 2
12 - Granulated sugar - 2.1 oz
13 - Cornstarch - 2 tbsp
14 - Vanilla extract - 1 tsp

# Preparation Steps:

01 - Preheat oven to 350°F. Line a 9-inch square baking pan with parchment paper, leaving an overhang 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 - In a large bowl, mix flour, oats, brown sugar, and salt. Rub in the cold butter with your fingers 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 form an even base. Reserve the remaining crumble for the 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 in the hot milk while whisking constantly. Return mixture to the pan and cook over medium heat, stirring, until thickened, approximately 2 to 3 minutes. Remove from heat and stir in vanilla extract.
07 - Spread the cooked rhubarb evenly over the baked base. Pour the custard layer over the rhubarb.
08 - Sprinkle the reserved crumble mixture evenly over the top.
09 - Bake for 30 minutes, or until the crumble 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 Advice:

01 -
  • Three distinct textures in every bite—buttery crumble, creamy custard, and jammy rhubarb—that somehow work together without fighting.
  • It looks impressive enough to bring to tea but honestly tastes even better when you sneak a piece straight from the pan while it's still warm.
  • Once you nail the custard layer, you'll find yourself making these bars constantly because they disappear faster than you'd expect.
02 -
  • Don't skip chilling the bars—warm custard is wobbly and nearly impossible to slice without everything collapsing into a delicious but messy pile.
  • If your custard looks grainy or broken, it usually means it got too hot or the temperature changed too rapidly; low and slow is the only way forward here.
03 -
  • Use the parchment paper overhang to lift the entire block out of the pan before slicing—this prevents damage and makes cleaning up incredibly easy.
  • If you don't have a pastry cutter, two butter knives or even a fork work perfectly for rubbing the butter into the flour until it resembles breadcrumbs.
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