Save on Pinterest My neighbor showed up one May morning with a shopping bag full of rhubarb stalks from her garden, more than she knew what to do with. I'd never baked with rhubarb before, but I remembered those old-fashioned rhubarb and custard sweets from childhood and thought, why not turn that into something I could slice and share? These bars came out of that experiment, and they've been my go-to spring treat ever since. The tartness of the rhubarb plays beautifully against the smooth vanilla custard, and the buttery crumble on top ties it all together.
I brought a batch to a village bake sale once, and they sold out before I even finished setting up the table. One woman told me they reminded her of her grandmother's rhubarb tart, but easier to eat with tea. That day, I realized these bars weren't just a dessert, they were a little edible memory for people. I've made them dozens of times since, and they never last long.
Ingredients
- Fresh rhubarb: Choose firm, bright stalks and trim away any leaves, as they're toxic. The tartness is what makes these bars sing.
- Granulated sugar (for rhubarb): This tames the rhubarb's sharpness without making it too sweet.
- Lemon juice: A little acidity brightens the rhubarb and keeps the flavor lively.
- Cornstarch (for rhubarb): It thickens the rhubarb mixture so it doesn't make the base soggy.
- All-purpose flour: The backbone of both the base and the crumble topping.
- Rolled oats: They add texture and a rustic, wholesome feel to the crumble.
- Unsalted butter: Cold butter is key, it creates those lovely crumbly bits when you rub it into the dry ingredients.
- Light brown sugar: Adds a hint of caramel flavor to the crumble that white sugar just can't match.
- Salt: A small amount balances the sweetness and deepens the overall flavor.
- Whole milk: The base of the custard, it makes it rich and creamy.
- Egg yolks: These thicken the custard and give it that classic golden color.
- Granulated sugar (for custard): Sweetens the custard just enough without overpowering the vanilla.
- Cornstarch (for custard): Helps the custard set so it slices neatly once chilled.
- Vanilla extract: A teaspoon of good vanilla makes the custard taste homemade and warm.
Instructions
- Prep Your Pan:
- Line your square pan with parchment, letting the edges hang over the sides. This little trick makes lifting out the bars so much easier later.
- Cook the Rhubarb:
- Combine the rhubarb, sugar, lemon juice, and cornstarch in a saucepan and cook over medium heat, stirring often. You'll know it's ready when the rhubarb breaks down and the mixture thickens into a jammy consistency, about 8 to 10 minutes.
- Make the Crumble Mix:
- In a large bowl, toss together the flour, oats, brown sugar, and salt. Rub the cold butter in with your fingertips until it looks like rough breadcrumbs, some bigger clumps are fine.
- Press the Base:
- Take about two-thirds of the crumble mixture and press it firmly into the bottom of your prepared pan. Set the rest aside for topping.
- Bake the Base:
- Pop the pan in the oven for 15 minutes until the base is lightly golden. Let it cool a bit while you make the custard.
- Prepare the Custard:
- Heat the milk in a saucepan until it's steaming. In a separate bowl, whisk the egg yolks, sugar, and cornstarch until smooth, then slowly pour in the hot milk, whisking constantly to avoid scrambling the eggs.
- Thicken the Custard:
- Return the mixture to the pan and cook over medium heat, stirring continuously, until it thickens enough to coat the back of a spoon. Stir in the vanilla and take it off the heat.
- Layer It Up:
- Spread the cooled rhubarb evenly over the baked base, then pour the custard gently over the rhubarb layer. Scatter the reserved crumble mixture on top.
- Bake Until Golden:
- Bake for 30 minutes, 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 refrigerate for at least 2 hours. Use the parchment overhang to lift them out and cut into 16 squares.
Save on Pinterest One afternoon, I served these bars to a friend who'd just moved to England from Spain. She'd never tasted rhubarb before and was skeptical at first, but after one bite she asked for the recipe. It reminded me that food has this quiet way of introducing us to new flavors and places, even in our own kitchens.
Storing and Serving
These bars keep beautifully in the fridge for up to three days in an airtight container. I like to serve them cold, straight from the fridge, but you can also let them sit at room temperature for 10 minutes if you prefer a softer crumble. A light dusting of powdered sugar or a small scoop of vanilla ice cream on the side turns them into a proper dessert.
Flavor Variations
If you want to play around with the rhubarb layer, try adding a handful of fresh raspberries or strawberries for extra sweetness and color. I've also stirred a pinch of ground ginger into the crumble mixture for a subtle warmth that pairs wonderfully with the tartness. Once, I swapped the vanilla extract for almond, and it gave the custard a marzipan-like flavor that my sister absolutely loved.
What to Watch For
The custard layer can look a bit wobbly when it comes out of the oven, and that's completely normal. It will set as it cools and chills. If your rhubarb is especially tart, you can add an extra tablespoon of sugar to the rhubarb mixture without throwing off the balance. Just be gentle when spreading the custard over the rhubarb so the layers stay distinct and pretty.
- Use fresh rhubarb if possible, frozen tends to release too much liquid.
- Press the base firmly so it doesn't crumble when you slice the bars.
- Let the bars chill fully before cutting for the neatest edges.
Save on Pinterest These bars have become one of those recipes I turn to when I want something impressive but not fussy. They taste like springtime in the English countryside, and every time I make them, someone asks for seconds.
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 layer from becoming too watery.
- → Why do the bars need to chill before cutting?
Chilling allows the custard layer to set completely, making it much easier to cut clean, neat bars without the layers sliding apart.
- → Can I make these bars ahead of time?
Absolutely. These bars can be made up to 3 days in advance and stored in the refrigerator in an airtight container.
- → What can I substitute for rhubarb?
Strawberries, raspberries, or a mix of berries work wonderfully. Adjust sugar to taste depending on the sweetness of your chosen fruit.
- → How do I know when the custard layer is properly set?
The custard should look slightly jiggly in the center when you gently shake the pan, but not liquid. It will firm up completely as it cools.
- → Can I freeze these bars?
Yes, wrap individual bars tightly in plastic wrap and freeze for up to 2 months. Thaw in the refrigerator before serving.