# Ingredient List:
→ 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 Prepare:
01 - Preheat oven to 350°F. Line a 9-inch square baking pan with parchment paper, allowing excess to overhang for easy removal.
02 - In a saucepan, combine chopped rhubarb, granulated sugar, lemon juice, and cornstarch. 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 mixing bowl, combine all-purpose flour, rolled oats, light brown sugar, and salt. Mix thoroughly until evenly distributed.
04 - Rub the cold cubed butter into the dry ingredients using your fingertips or a pastry cutter until the mixture resembles coarse breadcrumbs.
05 - Press two-thirds of the crumble mixture firmly into the bottom of the prepared baking pan to create an even, compact base. Reserve the remaining one-third for topping.
06 - Bake the base for 15 minutes until lightly golden. Remove from oven and allow to cool slightly.
07 - Heat whole milk in a saucepan until steaming but not boiling. In a separate bowl, whisk egg yolks, granulated sugar, and cornstarch until smooth and pale. Gradually pour the hot milk into the egg mixture while whisking constantly. Return the 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.
08 - Spread the cooled rhubarb filling evenly over the baked base layer. Pour the prepared custard layer over the rhubarb, spreading gently to ensure even coverage.
09 - Sprinkle the reserved crumble mixture evenly over the custard layer, covering the entire surface.
10 - Bake for 30 minutes, or until the crumble topping is golden and the custard layer is set but still slightly soft in the center.
11 - Allow the bars to cool completely in the baking pan, then refrigerate for a minimum of 2 hours before carefully lifting out using the parchment overhang and cutting into 16 equal portions.
