# 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 & 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
# Method:
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 8-10 minutes. Transfer to a bowl to cool.
03 - In a large mixing bowl, combine flour, oats, brown sugar, and salt. Rub in the cold cubed butter with your fingertips or pastry cutter until 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. Remove from oven and allow to cool briefly.
06 - Heat milk in a saucepan until steaming but not boiling. In a separate bowl, whisk together egg yolks, sugar, and cornstarch until smooth. Gradually pour hot milk into egg mixture while whisking constantly. Return combined mixture to saucepan and cook over medium heat, stirring continuously, until thickened, approximately 2-3 minutes. Remove from heat and stir in vanilla extract.
07 - Spread cooled rhubarb compote evenly over the baked base layer. Pour custard filling evenly over rhubarb.
08 - Sprinkle reserved crumble mixture evenly and generously over custard layer.
09 - Bake for 30 minutes, or until crumble is golden brown and custard is just set with slight movement in the center.
10 - Allow bars to cool completely in the pan at room temperature. Refrigerate for a minimum of 2 hours before lifting out using parchment overhang. Cut into 16 squares with a sharp knife dipped in hot water between cuts.
