# What You Need:
→ Rhubarb Layer
01 - Fresh rhubarb, trimmed and chopped - 14 oz
02 - Granulated sugar - 2.6 oz
03 - Fresh lemon juice - 1 tbsp
04 - Cornstarch - 1 tbsp
→ Shortbread Base and 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
# How To Make It:
01 - Preheat oven to 350°F. Line a 9-inch square baking pan with parchment paper, leaving an overhang for easy removal.
02 - In a saucepan, combine rhubarb, sugar, lemon juice, and cornstarch. Cook over medium heat, stirring often, until rhubarb softens and mixture thickens, approximately 8-10 minutes. Set aside to cool.
03 - In a large bowl, mix flour, oats, brown sugar, and salt. Rub in the cold butter with your fingers or a pastry cutter until the mixture resembles coarse crumbs.
04 - Press two-thirds of the crumble mixture firmly into the bottom of the prepared pan to form an even base. Reserve the remaining crumble for the topping.
05 - Bake for 15 minutes until lightly golden. Remove from oven and let cool slightly.
06 - In a saucepan, heat the milk until steaming but not boiling. In a bowl, whisk egg yolks, sugar, and cornstarch until smooth. Gradually pour the hot milk into the egg mixture, whisking constantly. Return mixture to the pan and cook over medium heat, stirring, until thickened, 2-3 minutes. Remove from heat and stir in vanilla.
07 - Spread the cooked rhubarb evenly over the baked base. Pour the custard layer over the rhubarb.
08 - Sprinkle the reserved crumble mixture evenly over the custard layer.
09 - Bake for 30 minutes, or until the crumble is golden and the custard is just set.
10 - Cool completely in the pan, then chill for at least 2 hours before lifting out and cutting into 16 bars.
