Save My neighbor dropped off a bundle of fresh rhubarb one Saturday morning, bright pink and impossibly tart. I had no plan for it, just a vague memory of my grandmother mentioning custard and crumble in the same breath. So I started layering: tangy fruit, silky vanilla custard, buttery oat topping. The kitchen smelled like spring bakery magic, and by the time they cooled, I had sixteen perfect bars that tasted like nostalgia I never actually had.
I brought these to a spring potluck once, and someone asked if I'd ordered them from a bakery. I laughed because the custard had split slightly while I whisked it, and I'd nearly panicked. But once everything baked together, the imperfections disappeared under that golden crumble. Sometimes the best compliments come from recipes that scared you a little.
Ingredients
- Fresh rhubarb: The star of the show, its tartness balances the sweetness perfectly, and chopping it into even pieces helps it cook down uniformly.
- Granulated sugar (for rhubarb): This tames the rhubarb's sharp edge without making it cloying, and a little lemon juice brightens everything.
- Cornstarch (for rhubarb): It thickens the fruit into a jammy layer that won't soak through the base.
- All-purpose flour: Forms the structure of both the base and the crumble, giving you that tender, crumbly bite.
- Rolled oats: They add texture and a subtle nuttiness that makes the crumble feel more rustic and interesting.
- Unsalted butter: Cold and cubed is key, it creates those crumbly pockets that turn golden and crisp in the oven.
- Light brown sugar: Its molasses notes deepen the flavor of the crumble and complement the rhubarb beautifully.
- Whole milk: The base of the custard, it needs to be full-fat for the creamiest, most luxurious texture.
- Egg yolks: They thicken the custard and give it that classic, velvety richness.
- Vanilla extract: A splash at the end makes the custard taste like the kind you remember from childhood desserts.
Instructions
- Prep Your Pan:
- Preheat your oven to 180°C and line a 23cm square pan with parchment, letting it hang over the edges. This overhang is your best friend when it's time to lift out the bars.
- Cook the Rhubarb:
- Combine rhubarb, sugar, lemon juice, and cornstarch in a saucepan over medium heat, stirring often until the rhubarb softens and the mixture thickens, about 8 to 10 minutes. Set it aside to cool while you work on the base.
- Make the Crumble:
- In a large bowl, mix flour, oats, brown sugar, and salt, then rub in the cold butter with your fingertips until it looks like coarse crumbs. It should clump when you squeeze it gently.
- Form the Base:
- Press two-thirds of the crumble mixture firmly into the bottom of your prepared pan to create an even, compact layer. Save the rest for topping.
- Bake the Base:
- Slide the pan into the oven for 15 minutes until the base is lightly golden. Let it cool slightly while you make the custard.
- Prepare the Custard:
- Heat the milk in a saucepan until it steams, then whisk together egg yolks, sugar, and cornstarch in a bowl until smooth. Gradually pour the hot milk into the yolk mixture, whisking constantly, then return everything to the pan and cook, stirring, until thickened (2 to 3 minutes). Stir in vanilla and remove from heat.
- Layer It Up:
- Spread the cooled rhubarb evenly over the baked base, then pour the warm custard over the rhubarb in an even layer. Work gently so the layers stay distinct.
- Add the Topping:
- Sprinkle the reserved crumble mixture evenly over the custard layer. Don't press it down, just let it sit on top.
- Bake Until Golden:
- Bake for 30 minutes, or until the crumble is golden and the custard is just set with a slight jiggle in the center. It will firm up as it cools.
- Cool and Chill:
- Let the bars cool completely in the pan, then chill in the fridge for at least 2 hours before lifting out by the parchment overhang and cutting into squares.
Save I served these at a spring tea party, and my friend who claims she doesn't like rhubarb ate three. She said it was the custard that won her over, that creamy middle layer that made the tartness feel like part of a conversation instead of a confrontation. I've been making them every May since.
Storing and Serving
These bars keep beautifully in the fridge for up to three days, covered loosely with plastic wrap or stored in an airtight container. I like them cold, straight from the fridge, but you can let them sit at room temperature for 10 minutes if you prefer a softer crumble. A dusting of powdered sugar or a scoop of vanilla ice cream on the side makes them feel extra special.
Customizing Your Bars
If your rhubarb is particularly tart, you can add a handful of raspberries or strawberries to the fruit layer for a sweeter, more complex flavor. Some people like to add a pinch of cinnamon or cardamom to the crumble mixture, which gives it a warm, spiced edge. You can also swap the oats for chopped almonds if you want a nuttier topping, just keep an eye on the bake time so they don't burn.
Troubleshooting Common Issues
If your custard splits or looks grainy, it means it got too hot too fast, so next time keep the heat medium-low and whisk constantly. If the bars are too soft to cut cleanly, they probably didn't chill long enough, so give them another hour in the fridge. If the crumble topping is browning too quickly, tent the pan loosely with foil for the last 10 minutes of baking.
- Always let the rhubarb cool before layering or it will melt the custard.
- Press the base firmly so it doesn't crumble apart when you slice the bars.
- Cut with a sharp knife wiped clean between slices for the neatest edges.
Save These bars are the kind of dessert that makes people linger at the table, asking for the recipe and sneaking second helpings. They are worth every layer, every chill, every bite.
Recipe Questions & Answers
- → Can I use frozen rhubarb instead of fresh?
Yes, frozen rhubarb works well. Thaw and drain excess liquid before cooking to prevent the bars from becoming too watery. You may need to cook it slightly longer to achieve the right consistency.
- → How do I know when the custard layer is properly set?
The custard should be just set with a slight wobble in the center when you gently shake the pan. It will firm up further as it cools and chills in the refrigerator.
- → Can I make these bars ahead of time?
Absolutely. These bars are excellent make-ahead treats. Prepare them up to 2 days in advance and store covered in the refrigerator. They actually taste better after chilling overnight.
- → What can I substitute for rhubarb if it's not in season?
Try using tart berries like raspberries, blackberries, or a combination. You can also use tart apples or plums. Adjust the sugar based on the sweetness of your chosen fruit.
- → Why is my crumble topping not crispy?
Ensure your butter is very cold when making the crumble, and avoid over-mixing. The mixture should resemble coarse breadcrumbs. Also, make sure to bake until golden brown for optimal crispness.
- → Can I freeze these bars?
Yes, these bars freeze well. Wrap individual bars tightly in plastic wrap and place in an airtight container. Freeze for up to 2 months. Thaw in the refrigerator overnight before serving.