Rhubarb and Custard Crumble Bars (Printable)

Tangy rhubarb and vanilla custard bars with buttery crumble topping. A delightful British springtime bake.

# What You'll Need:

→ 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

# Directions:

01 - Preheat oven to 350°F. Line a 9-inch square baking pan with parchment paper, leaving an overhang for easy removal.
02 - In a saucepan, combine rhubarb, sugar, lemon juice, and cornstarch. Cook over medium heat, stirring often, until rhubarb softens and mixture thickens, approximately 8-10 minutes. Set aside to cool.
03 - In a large bowl, combine flour, oats, brown sugar, and salt. Rub in the cold butter with your fingers or a pastry cutter until the mixture resembles coarse crumbs.
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 let cool slightly.
06 - In a saucepan, heat milk until steaming but not boiling. In a bowl, whisk egg yolks, sugar, and cornstarch until smooth. Gradually pour in the hot milk, whisking constantly. Return mixture to the pan and cook over medium heat, stirring, until thickened, approximately 2-3 minutes. Remove from heat and stir in vanilla.
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 chill for at least 2 hours before lifting out and cutting into bars.

# Expert Tips:

01 -
  • The tangy rhubarb cuts right through the sweetness, so it never feels heavy or cloying.
  • You get three textures in one bite: crumbly, creamy, and jammy all at once.
  • They slice cleanly after chilling, which makes them perfect for sharing or wrapping up as gifts.
  • The custard layer tastes like proper British dessert, not the boxed kind.
02 -
  • Don't skip chilling the bars, they will fall apart if you try to cut them warm.
  • If your rhubarb is especially watery, cook it a bit longer until it's thick and jammy, or the custard layer will get soupy.
  • Use cold butter for the crumble or it will turn greasy instead of crumbly.
03 -
  • Make the rhubarb layer the day before and keep it in the fridge, it saves time and the flavor deepens overnight.
  • If you want extra crumble on top, make half again as much and freeze the extra for next time.
  • Line your pan well and leave long parchment handles, lifting the whole block out in one piece makes slicing so much easier.
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