Rhubarb and Custard Crumble Bars (Print)

Tangy rhubarb meets creamy vanilla custard under a golden buttery crumble topping for the perfect springtime treat.

# Components:

→ Rhubarb Layer

01 - 14 oz fresh rhubarb, trimmed and chopped
02 - 6 tablespoons granulated sugar
03 - 1 tablespoon fresh lemon juice
04 - 1 tablespoon cornstarch

→ Shortbread Base and Crumble

05 - 2 cups all-purpose flour
06 - 1 cup rolled oats
07 - 10 tablespoons unsalted butter, cold and cubed
08 - 3/4 cup light brown sugar
09 - 1/2 teaspoon salt

→ Custard Layer

10 - 1 1/4 cups whole milk
11 - 2 large egg yolks
12 - 1/4 cup 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 overhang on sides for easy removal.
02 - In a saucepan, combine rhubarb, sugar, lemon juice, and cornstarch. Cook over medium heat, stirring frequently, until rhubarb softens and mixture thickens, approximately 8 to 10 minutes. Transfer to a bowl and allow to cool.
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.
04 - Press two-thirds of the crumble mixture firmly into the bottom of the prepared pan to create an even, compact base. Reserve the remaining crumble for topping.
05 - Bake the base for 15 minutes until lightly golden brown. Remove from oven and allow to cool slightly before proceeding.
06 - Heat milk in a saucepan until steaming but not boiling. In a separate bowl, whisk together egg yolks, sugar, and cornstarch until smooth and pale. Slowly pour hot milk into egg mixture while whisking constantly. Return combined mixture to the 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 the cooled rhubarb mixture evenly over the baked base. Pour the custard layer carefully over the rhubarb.
08 - Sprinkle the reserved crumble mixture evenly across the top layer.
09 - Bake for 30 minutes, or until the crumble topping is golden brown and the custard layer is just set but not overcooked.
10 - Allow the pan to cool completely at room temperature, then refrigerate for a minimum of 2 hours. Using the parchment paper overhang, lift the entire slab from the pan and cut into 16 equal bars.

# Expert Advice:

01 -
  • It's three desserts stacked into one pan, so everyone gets their texture fix in a single bite.
  • The tartness of rhubarb keeps these from feeling overly sweet, making them dangerously easy to eat more than one.
  • You can prep the rhubarb and crumble mixture the night before, which means stress-free entertaining.
02 -
  • Don't skip the initial bake of the base layer; it prevents the bottom from staying doughy and absorbing too much moisture from the rhubarb.
  • The custard will seem too thin when you first make it, but it firms up beautifully as it cools—trust the process and don't overcook it or you'll end up with grainy scrambled eggs.
  • Rhubarb varies wildly in tartness depending on the season, so taste as you cook and adjust sugar if needed.
03 -
  • Make the rhubarb compote and crumble mixture the day before and store them separately—this cuts prep time dramatically on baking day.
  • If your custard breaks or looks grainy, strain it through a fine sieve into a clean bowl; it won't be perfect, but it'll still taste wonderful.
  • Brown butter instead of regular butter in the crumble mixture adds a subtle nuttiness that feels almost professional.
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