Save There's something about the smell of rhubarb bubbling on the stove that pulls me straight back to early spring mornings in my tiny kitchen. I'd bought a bundle of bright pink stalks on a whim from the farmers' market, not entirely sure what I'd do with them. Then I remembered those old-fashioned rhubarb and custard sweets my grandmother used to keep in a glass jar, and I thought: what if I could turn that into something you could slice and share? These bars were born from that experiment, and they've become my go-to whenever I want to impress without fussing over individual servings.
I brought a pan of these to a spring garden party last year, and they disappeared faster than anything else on the table. A friend's mum told me they reminded her of her childhood, and she asked for the recipe three times before the afternoon was over. I love how food can do that, unlock a memory someone didn't even know they were carrying. That day, I realized these bars weren't just dessert, they were little edible time machines.
Ingredients
- Fresh rhubarb: The star of the show, its tartness is what makes these bars sing, so don't skimp on quality or try to substitute with frozen unless you drain it really well.
- Granulated sugar (for rhubarb): Just enough to tame the rhubarb's sharpness without turning it into candy, let the fruit stay a little feisty.
- Lemon juice: Brightens the rhubarb and helps it break down into a thick, spreadable layer that won't make the base soggy.
- Cornstarch (for rhubarb): This is your insurance against a runny filling, it thickens everything so the layers stay distinct.
- All-purpose flour: The backbone of both the base and the crumble, it gives structure without being heavy.
- Rolled oats: They add a nutty chew to the crumble and make it feel a bit more rustic and homemade.
- Unsalted butter: Cold and cubed is key, it creates those crumbly pockets that turn golden and crisp in the oven.
- Light brown sugar: Its slight molasses note adds warmth and depth to the crumble that white sugar just can't match.
- Salt: A small pinch balances all the sweetness and makes every other flavor more vivid.
- Whole milk: The base of the custard, full-fat is best for that rich, velvety texture.
- Egg yolks: They thicken the custard and give it that classic pale yellow color, save the whites for meringues later.
- Granulated sugar (for custard): Sweetens and helps the custard set without making it grainy.
- Cornstarch (for custard): A little cornstarch stabilizes the custard so it slices cleanly once chilled, no curdling or weeping.
- Vanilla extract: The final whisper of flavor that ties the whole thing together, use the real stuff if you can.
Instructions
- Prep Your Pan:
- Preheat your oven to 180°C and line a 23cm square pan with parchment, letting the edges hang over like little handles. This makes lifting the bars out later so much easier, trust me.
- Cook the Rhubarb:
- Combine rhubarb, sugar, lemon juice, and cornstarch in a saucepan and cook over medium heat, stirring often, until the rhubarb softens and the mixture thickens into a jammy consistency, 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 breadcrumbs. It should clump when you squeeze it but still feel sandy.
- Form the Base:
- Press two-thirds of the crumble firmly into the bottom of your lined pan to create an even layer. Reserve the rest for the topping.
- Bake the Base:
- Bake for 15 minutes until it's lightly golden and smells buttery. Pull it out and let it cool slightly while you make the custard.
- Prepare the Custard:
- Heat the milk in a saucepan until it's steaming, then whisk together egg yolks, sugar, and cornstarch in a bowl until smooth. Slowly pour the hot milk into the yolk mixture, whisking constantly, then return everything to the pan and cook over medium heat, stirring, until it thickens like pudding, about 2 to 3 minutes. Stir in the vanilla off the heat.
- Layer It Up:
- Spread the cooled rhubarb evenly over the baked base, then pour the warm custard over the top. Work gently so the layers stay distinct.
- Add the Crumble 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 brown and the custard is just set but still has a slight wobble in the center. It will firm up as it cools.
- Chill and Slice:
- Let the bars cool completely in the pan, then chill in the fridge for at least 2 hours before lifting out and cutting into squares. Cold bars slice much cleaner than warm ones.
Save I remember slicing into these for the first time and seeing those three perfect layers stacked up like a little edible sunset. The pink rhubarb, the pale custard, the golden crumble. It felt like a small triumph, like I'd managed to bottle up the best parts of spring and put them on a plate. My partner took one bite and declared them better than anything we'd ever bought from a bakery, and I think that's the moment I fell in love with these bars for good.
Storing and Serving
These bars keep beautifully in the fridge for up to three days, covered loosely with foil or in an airtight container. I like to serve them cold, straight from the fridge, with a light dusting of powdered sugar or a dollop of whipped cream. They're also lovely with a scoop of vanilla ice cream if you're feeling indulgent, the contrast between cold ice cream and the chilled custard is unexpectedly delightful.
Variations and Swaps
If you want a bit more tartness, toss in a handful of fresh raspberries with the rhubarb, they add little pockets of jammy sweetness. You can also swap the oats for chopped almonds in the crumble for a nuttier texture. I've even tried adding a pinch of cardamom to the custard once, and it gave the whole thing a subtle, aromatic lift that felt a bit exotic. Don't be afraid to play around, this recipe is more forgiving than it looks.
Troubleshooting Tips
If your custard seems too runny, don't panic, it will firm up as it chills. If it's lumpy, you probably added the hot milk too quickly, next time whisk more slowly and steadily. If the crumble topping is browning too fast, tent the pan loosely with foil for the last 10 minutes of baking.
- Use a sharp knife dipped in hot water to get clean slices, wipe it between cuts.
- If the base feels too hard, you might have pressed it too firmly, aim for compact but not concrete.
- Let the rhubarb cool before layering or it can melt the base slightly and make things messy.
Save These bars have become one of those recipes I turn to when I want to feel proud of what I've made, without spending all day in the kitchen. I hope they bring you as much joy as they've brought me.
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 appear just set but still slightly wobbly 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 ideal for making ahead. They keep well in the refrigerator for up to 3 days and actually taste better after chilling for at least 2 hours, allowing the layers to set properly.
- → What can I substitute for rhubarb if it's not in season?
Try using tart fruits like gooseberries, sour cherries, or a mix of raspberries and strawberries. Adjust sugar levels based on the sweetness of your chosen fruit.
- → Why is my crumble topping not crispy?
Ensure your butter is cold when making the crumble mixture. If the topping becomes soggy after cooling, this is normal due to the moist custard layer beneath. The texture should be pleasantly soft rather than crunchy.
- → Can I freeze these bars?
Yes, these bars freeze well for up to 2 months. Wrap individual portions tightly in plastic wrap and foil. Thaw in the refrigerator overnight before serving.