# 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 - 2 cups all-purpose flour
06 - 1 cup rolled oats
07 - 5.3 oz unsalted butter, cold and cubed
08 - 3.5 oz light brown sugar
09 - 1/2 teaspoon salt
→ Custard Layer
10 - 1.25 cups 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 - In a saucepan, combine chopped rhubarb, sugar, lemon juice, and cornstarch. Cook over medium heat, stirring frequently, until rhubarb softens and mixture thickens, approximately 8-10 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, work in the cold cubed butter until the mixture resembles coarse breadcrumbs.
04 - Press two-thirds of the crumble mixture firmly and evenly into the bottom of the prepared pan. Reserve remaining crumble for topping.
05 - Bake the base for 15 minutes until lightly golden in color. Remove from oven and allow to cool slightly.
06 - Heat milk in a saucepan until steaming but not boiling. In a separate bowl, whisk together egg yolks, sugar, and cornstarch until smooth. Slowly 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 2-3 minutes. Remove from heat and stir in vanilla extract.
07 - Spread the cooled rhubarb filling evenly over the baked base. Pour the custard layer over the rhubarb, distributing it uniformly.
08 - Sprinkle the reserved crumble mixture evenly across the custard layer.
09 - Bake for 30 minutes, or until the crumble is golden brown and the custard layer is just set but still slightly tender.
10 - Allow the bars to cool completely in the pan, then refrigerate for at least 2 hours. Lift out using parchment paper overhang and cut into 16 equal bars.
