# What You'll 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 and Crumble
05 - 2 cups all-purpose flour
06 - 1 cup rolled oats
07 - 10.6 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 rhubarb, 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 bowl, combine flour, oats, brown sugar, and salt. Rub in cold butter using your fingertips or a pastry cutter until texture resembles coarse crumbs.
04 - Press two-thirds of the crumble mixture firmly into the prepared pan to create an even base. Reserve remaining crumble for topping. Bake base for 15 minutes until lightly golden. Remove from oven and allow to cool slightly.
05 - In a saucepan, heat milk until steaming but not boiling. In a bowl, whisk egg yolks, sugar, and cornstarch until smooth. Gradually pour hot milk into egg mixture while whisking constantly. Return mixture to saucepan and cook over medium heat, stirring continuously, until thickened, approximately 2 to 3 minutes. Remove from heat and stir in vanilla extract.
06 - Spread cooled rhubarb evenly over baked base. Pour custard layer over rhubarb, spreading evenly.
07 - Sprinkle reserved crumble mixture evenly across custard layer.
08 - Bake for 30 minutes, or until crumble is golden brown and custard is just set.
09 - Cool completely in pan, then refrigerate for at least 2 hours before lifting out and cutting into 16 bars.
