# What You'll Need:
→ Rhubarb Layer
01 - Fresh rhubarb, trimmed and chopped, 14 oz
02 - Granulated sugar, 5.3 oz
03 - Lemon juice, 1 tbsp
04 - Cornstarch, 1 tbsp
→ Shortbread Base & Crumble
05 - All-purpose flour, 8.8 oz
06 - Rolled oats, 3.5 oz
07 - Unsalted butter, cold and cubed, 5.3 oz
08 - Light brown sugar, 3.5 oz
09 - Salt, 1/2 tsp
→ Custard Layer
10 - Whole milk, 10.1 fl oz
11 - Large egg yolks, 2
12 - Granulated sugar, 2.1 oz
13 - Cornstarch, 2 tbsp
14 - Vanilla extract, 1 tsp
# Cooking Steps:
01 - Preheat oven to 350°F. Line a 9-inch square baking pan with parchment paper, leaving overhang on sides for easy removal.
02 - Combine rhubarb, sugar, lemon juice, and cornstarch in a saucepan. 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 - Mix flour, oats, brown sugar, and salt in a large bowl. Using your fingers or a pastry cutter, rub in cold butter until mixture resembles coarse breadcrumbs.
04 - Press two-thirds of crumble mixture firmly and evenly into prepared pan to create a compact base. Reserve remaining crumble for topping.
05 - Bake base for 15 minutes until lightly golden. Remove from oven and allow to cool slightly.
06 - Heat milk in saucepan until steaming but not boiling. In a separate bowl, whisk egg yolks, sugar, and cornstarch until smooth. Gradually pour hot milk into egg mixture, whisking constantly. Return combined 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.
07 - Spread cooled rhubarb evenly over baked base. Pour custard layer over rhubarb, spreading to cover completely.
08 - Distribute reserved crumble mixture evenly across custard layer.
09 - Bake for 30 minutes until crumble is golden and custard is set but still slightly soft in center.
10 - Allow bars to cool completely in pan. Refrigerate for at least 2 hours. Lift from pan using parchment overhang and cut into 16 equal portions.
