# What You'll Need:
→ Rhubarb Layer
01 - 14 oz fresh rhubarb, trimmed and chopped
02 - 1/3 cup granulated sugar
03 - 1 tbsp lemon juice
04 - 1 tbsp cornstarch
→ Shortbread Base & Crumble
05 - 2 cups all-purpose flour
06 - 1 cup rolled oats
07 - 2/3 cup unsalted butter, cold and cubed
08 - 1/2 cup light brown sugar, packed
09 - 1/2 tsp salt
→ Custard Layer
10 - 1 1/4 cups whole milk
11 - 2 large egg yolks
12 - 1/4 cup granulated sugar
13 - 2 tbsp cornstarch
14 - 1 tsp vanilla extract
# Directions:
01 - Preheat oven to 350°F. Line a 9-inch square baking pan with parchment paper, leaving an overhang for easy removal.
02 - Combine rhubarb, granulated 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. Set aside to cool.
03 - Mix flour, oats, brown sugar, and salt in a large bowl. Rub in cold butter using fingers or a pastry cutter until mixture resembles coarse crumbs.
04 - Press two-thirds of the crumble mixture firmly into the bottom of the prepared pan to create an even base. Reserve remaining mixture for topping.
05 - Bake the base for 15 minutes until lightly golden. Remove from oven and let cool slightly.
06 - Heat milk in a saucepan until steaming but not boiling. Whisk egg yolks, sugar, and cornstarch in a bowl until smooth. Gradually whisk in hot milk. Return mixture to pan and cook over medium heat, stirring constantly, until thickened, 2 to 3 minutes. Remove from heat and stir in vanilla.
07 - Spread cooked rhubarb evenly over the baked base. Pour custard layer over the rhubarb.
08 - Sprinkle reserved crumble mixture evenly over the custard layer.
09 - Bake for 30 minutes until crumble is golden and custard is just set.
10 - Cool completely in the pan. Refrigerate for at least 2 hours before lifting out and cutting into 16 bars.
