📖 Instructions

1. Get Started: Preheat your oven to 350°F (175°C). Lightly grease a 9x13 inch baking pan. Don't skip this step – a greased pan prevents sticking and makes cleanup a breeze!
2. Make the Crust: In a large mixing bowl, whisk together 2 cups all-purpose flour, 1/2 cup granulated sugar, and 1/4 teaspoon salt.
3. Add the Butter: Cut in 1 cup (2 sticks) of cold, unsalted butter into the flour mixture using a pastry blender or your fingertips, until the mixture resembles coarse crumbs. This is crucial for a flaky crust – keep that butter cold!
4. Bind the Crust: Add 1 large egg, beaten, to the mixture. Mix until the dough just comes together. It should be slightly crumbly but hold its shape when pressed.
5. Press the Crust: Press the dough evenly into the prepared baking pan. Use the bottom of a measuring cup to flatten it and create a smooth surface.
6. Pre-bake the Crust: Bake the crust for 15 minutes, or until it's lightly golden. Keep an eye on it – you want it set but not overly browned.
7. Prepare the Custard Filling: While the crust is baking, make the custard. In a separate mixing bowl, whisk together 3 large eggs, 3/4 cup granulated sugar, 1/4 cup all-purpose flour, 1/4 teaspoon salt, and 1 teaspoon vanilla extract until smooth.
8. Add the Dairy: Gradually whisk in 1 1/2 cups heavy cream and 1/2 cup milk until well combined. The mixture should be smooth and creamy.
9. Prepare the Rhubarb: In a medium bowl, toss 2 cups of chopped rhubarb with 2 tablespoons of granulated sugar. This helps to draw out some of the moisture from the rhubarb and sweeten it slightly.
10. Assemble the Bars: Remove the pre-baked crust from the oven. Pour the custard filling evenly over the crust.
11. Add the Rhubarb: Sprinkle the sugared rhubarb evenly over the custard filling. Arrange the pieces so they are nicely distributed.
12. Bake the Bars: Bake for 35-40 minutes, or until the custard is set and the top is lightly golden. The center should be just slightly jiggly. If the crust starts to brown too quickly, tent the pan with foil.
13. Cool and Chill: Let the bars cool completely in the pan on a wire rack. Then, refrigerate for at least 2 hours before cutting into squares. This chilling step is important – it allows the custard to fully set and makes cutting easier.
14. Cut and Serve: Cut the slab bars into squares and serve chilled. A dusting of powdered sugar is optional but adds a lovely finishing touch.