Rhubarb Custard Crumble Bars

My grandmother grew rhubarb in that stubborn corner of her garden where nothing else seemed to thrive. Every spring, shed hand me the basket and tell me the reddest stalks made the sweetest pies. I remember standing in her kitchen watching her transform those tart, crimson stalks into something magical, always with a little patience and lot of butter. These bars capture that same memory but with the added comfort of creamy custard nestled beneath the crumble.

Last spring, I made these for a neighborhood gathering and watched them disappear in record time. My friend Sarah, whod sworn she disliked rhubarb since childhood, took one bite and asked for the recipe before shed even finished her first bar. Thats the thing about these layered beauties they convert skeptics without trying.

Ingredients

• 400 g fresh rhubarb: Choose stalks that are firm and brightly colored, avoiding any that are too thick or woody as they can be stringy
• 75 g granulated sugar: Adjust slightly based on how tart your rhubarb is, tasting as you cook the filling
• 1 tbsp lemon juice: This brightens the rhubarb and helps preserve its lovely pink color during cooking
• 1 tbsp cornstarch: Essential for thickening the rhubarb into a spreadable layer that wont make the base soggy
• 250 g all-purpose flour: Provides structure to both the base and crumble layers
• 100 g rolled oats: Adds wonderful texture and that familiar crumble bite we all love
• 150 g unsalted butter: Keep this cold when working with the crumble mixture for the best texture
• 100 g light brown sugar: Gives the crumble a deeper, caramel note that pairs beautifully with the fruit
• 1/2 tsp salt: Balances the sweetness and enhances all the flavors
• 300 ml whole milk: Creates a rich, creamy custard layer that sets properly when chilled
• 2 large egg yolks: These provide richness and help the custard thicken beautifully
• 60 g granulated sugar: Sweetens the custard without overpowering the rhubarb
• 2 tbsp cornstarch: Ensures the custard layer holds its shape when sliced
• 1 tsp vanilla extract: Use pure vanilla extract for the best flavor, it really shines through

Instructions

Prepare the oven and pan:

Preheat your oven to 180°C (350°F) and line a 23cm square baking pan with parchment paper, leaving those overhangs like little handles to help lift the bars out later.

Cook the rhubarb filling:

Combine the rhubarb, sugar, lemon juice, and cornstarch in a saucepan over medium heat, stirring frequently until the rhubarb softens and the mixture thickens nicely, about 8 to 10 minutes. Set this aside to cool while you prepare everything else.

Make the crumble mixture:

Mix the flour, oats, brown sugar, and salt in a large bowl, then rub in the cold butter with your fingers until the mixture looks like coarse crumbs with some pea-sized pieces remaining.

Press in the base:

Take two-thirds of your crumble mixture and press it firmly and evenly into the bottom of your prepared pan, using the back of a spoon or measuring cup to compact it well.

Par-bake the base:

Bake for 15 minutes until lightly golden, then remove from the oven and let it cool slightly while you make the custard layer.

Prepare the custard:

Heat the milk in a saucepan until steaming but not boiling, then whisk your egg yolks, sugar, and cornstarch until smooth before gradually whisking in the hot milk. Return everything to the pan and cook over medium heat, stirring constantly, until thickened, about 2 to 3 minutes, then stir in the vanilla.

Layer everything:

Spread the cooled rhubarb evenly over your baked base, pour the custard over the rhubarb, and sprinkle the remaining crumble mixture across the top.

Bake to golden perfection:

Bake for 30 minutes until the crumble is golden brown and the custard is just set, with a slight wobble in the center.

Chill thoroughly:

Let the bars cool completely in the pan, then refrigerate for at least 2 hours until firm before lifting out using the parchment handles and cutting into squares.

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Ive learned that the best rhubarb season is short, so I try to make these bars as often as possible during those few precious weeks. Theres something deeply satisfying about using up every last stalk from the garden in a recipe that feels like a hug in dessert form.

Getting the Texture Right

The key to these bars is the contrast between the soft custard, tender rhubarb, and crunchy crumble. Ive found that pressing the base firmly with the bottom of a measuring cup creates an even foundation that bakes up perfectly supportive.

Working with Rhubarb

Fresh rhubarb varies wildly in sweetness, so taste your cooked filling before layering it. If its too tart, dont hesitate to add another tablespoon of sugar. The goal is balance, not pucker.

Make Ahead and Storage

These bars actually improve after a day in the refrigerator, as the flavors meld together beautifully. They keep well for up to three days, though they rarely last that long in my house.

• Wrap the uncut slab tightly in foil and freeze for up to a month
• Let frozen bars thaw overnight in the refrigerator before serving
• Serve slightly chilled rather than room temperature for the best texture

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These bars have become my go-to for spring gatherings, and I hope they find their way into your regular rotation too. Theres nothing quite like that first bite of tangy sweet comfort.

Frequently Asked Questions

→ How do I prevent the rhubarb layer from being too watery?

Ensure you cook the rhubarb with cornstarch until it thickens sufficiently. This helps bind the juices and prevents a soggy bar, ensuring a firm and flavorful fruit layer.

→ Can I use frozen rhubarb for this dish?

Yes, you can use frozen rhubarb. Thaw it completely and drain any excess liquid before cooking it with the sugar, lemon juice, and cornstarch as per the instructions.

→ How long will these bars stay fresh?

When stored in an airtight container in the refrigerator, these delicious bars will maintain their freshness and best texture for up to 3 days.

→ What's the best way to cut clean, neat slices?

For neat slices, make sure the bars are thoroughly chilled for at least 2 hours, or preferably overnight, before lifting them from the pan and cutting. Using a warm, clean knife can also help.

→ Can I make this dessert with a different fruit?

Absolutely. While rhubarb offers a unique tang, you could experiment with other fruits like berries, apples, or peaches. Adjust the sugar and cornstarch as needed to achieve the right consistency for your chosen fruit.