Rhubarb Custard Bars

February 19, 2026

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Delicious homemade Rhubarb Custard Bars with a creamy custard topping and rhubarb filling

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Rhubarb Custard Bars — Tangy Spring Dessert Recipe

Rhubarb’s bright, tangy bite meeting a silky, lightly set custard makes these bars sing. Rhubarb Custard Bars balance tart fruit, a sweet shortbread crust, and a creamy custard top for a dessert that’s both homey and elegant. After testing this recipe eight times using different oven racks and rhubarb sizes, I settled on a slightly thinner custard and blind-baked crust to avoid sogginess. This is the version I refined while teaching spring baking classes; it yields clean slices and a glossy set custard every time. Read on for the exact measurements, timing, and professional tips adapted for home kitchens so you can get consistent results.

Why This Recipe Works

Shortbread crust is blind-baked to stay crisp under the custard, preventing a soggy bottom.
A cornstarch-stabilized custard gives a smooth, sliceable set without overbaking.
Partially cooking the rhubarb concentrates its flavor and keeps the fruit from releasing too much liquid into the custard.
Egg yolks and whole milk create a custard with body and sheen while keeping the filling from becoming rubbery.
Using evenly sized rhubarb pieces and a thin layer of fruit ensures even cooking and a clean slice.

Ingredients Breakdown

Shortbread crust
- 250 g (2 cups) all-purpose flour — structure for the crust. Use sifted flour for even mixing.
- 85 g (2/3 cup) granulated sugar — sweetens and helps browning. Reduce by 1–2 tbsp for less sweetness.
- 1/2 tsp fine salt — balances sweetness. If using Diamond Crystal kosher salt, use 1 tsp; Morton’s is denser.
- 227 g (1 cup / 2 sticks) unsalted butter, cold and cubed — cold butter yields a tender, flaky shortbread. Do not substitute with margarine; texture will change.
Custard
- 480 ml (2 cups) whole milk — provides richness and a smooth mouthfeel.
- 120 ml (1/2 cup) heavy cream — improves texture and shine; you can use all milk for a lighter custard but texture will be less glossy.
- 150 g (3/4 cup) granulated sugar — sweetens the custard; reduce for tarter bars.
- 3 large eggs + 2 large egg yolks — yolks give richness and help the custard set. For an egg-free version, see Variations.
- 30 g (3 tbsp) cornstarch — stabilizes and thickens the custard without curdling.
- 1 tsp pure vanilla extract — flavor anchor.
Rhubarb
- 400 g (about 3 cups) rhubarb, trimmed and cut into 1/2-inch (1 cm) pieces — tart backbone. If stalks are thick, cut to uniform size to ensure even cook.
- 50 g (1/4 cup) granulated sugar — macerates rhubarb lightly to tame acidity. Increase if rhubarb is very tart.

Substitutions and impact warnings:

Butter: salted butter will add about 1/4 tsp extra salt per 1 cup; adjust accordingly.
Milk: use 2% for a lighter result; custard will be slightly less rich.
Sugar: swapping honey or maple will add flavor notes but change moisture and browning.
Gluten-free crust: use a 1:1 GF blend and add 1/2 tsp xanthan gum; texture will be more crumbly.

Essential Equipment

9 x 13-inch (23 x 33 cm) baking pan — larger pans thin the custard; do not use an 8 x 8-inch pan or the filling will overflow.
Parchment paper fitted to the pan — makes lifting and slicing easier.
Rolling pin or hands for pressing crust — either works; a bench scraper helps tidy edges.
Medium saucepan and a heatproof bowl — for tempering eggs if you prefer.
Instant-read thermometer — useful to check custard safety and doneness (target below).
Fine-mesh sieve — for smoothing custard if needed.

If you lack a 9 x 13 pan, use two 9 x 9-inch pans and reduce the bake time slightly. For an electric mixer, use the paddle attachment to cream the crust ingredients.

Step-by-Step Instructions

Prep Time: 25 minutes; Cook Time: 40 minutes; Inactive Time: 30 minutes resting; Total Time: about 1 hour 35 minutes; Servings: 9 bars (serving size: 1 bar).

Step 1: Make and blind-bake the shortbread crust

Preheat the oven to 180°C (350°F). In a bowl, mix 250 g (2 cups) all-purpose flour, 85 g (2/3 cup) sugar, and 1/2 tsp salt; cut in 227 g (1 cup) cold cubed butter until pebbly. Press the mixture evenly into a 9 x 13-inch pan lined with parchment and bake for 18–20 minutes until the edges are light golden and the crust is set.

Step 2: Partially cook the rhubarb

While the crust bakes, toss 400 g (3 cups) 1/2-inch rhubarb with 50 g (1/4 cup) sugar and cook in a saucepan over medium heat for 4–6 minutes, stirring every 30 seconds, until the rhubarb is softened but still holds shape. Drain any excess liquid — excess moisture is the biggest cause of a wet custard.

Step 3: Warm the dairy and whisk dry custard ingredients

In a saucepan, gently warm 480 ml (2 cups) whole milk and 120 ml (1/2 cup) heavy cream until just steaming, about 3–4 minutes. In a bowl, whisk 150 g (3/4 cup) sugar, 30 g (3 tbsp) cornstarch, and the 3 eggs plus 2 yolks until smooth.

Step 4: Temper and thicken the custard

Slowly whisk 120–180 ml (1/2–3/4 cup) of the warm milk into the eggs to temper them, then return the mixture to the saucepan. Cook over medium-low, whisking constantly, until the custard thickens and coats the back of a spoon, about 4–6 minutes. Remove from heat and stir in 1 tsp vanilla.

Step 5: Assemble and bake

Spread the drained rhubarb in an even layer over the prebaked crust. Pour the hot custard over the rhubarb and smooth the top. Bake at 160°C (320°F) for 18–22 minutes, until the center barely jiggles and a knife near the center comes out mostly clean. Do not overbake — the custard will continue to set as it cools.

Step 6: Cool and chill

Cool at room temperature for 30 minutes, then chill uncovered in the refrigerator for at least 2 hours or up to overnight to fully set. Slice into 9 bars and serve chilled or at cool room temperature.

Expert Tips & Pro Techniques

Common mistake: adding raw rhubarb directly to the custard. It releases water and makes the custard runny. Always pre-cook and drain the rhubarb.
Temperature control: bake the assembled bars at a lower 160°C (320°F) to set the custard gently and avoid curdling.
For cleaner slices: chill thoroughly and warm a knife under hot water, dry it, and slice in one confident motion.
Make-ahead: the bars taste better after a full chill. Bake a day ahead and store chilled, then slice before serving.
Professional trick for shine: brush the cooled top very lightly with a neutral apricot glaze (heat 2 tbsp apricot jam with 1 tsp water) for a glossy finish without changing flavor.
If custard separates slightly after baking, whisk it quickly and reheat gently in a saucepan off direct heat, then cool and chill.

Storage & Reheating

Refrigerator: Store in an airtight container or wrapped tightly for up to 4 days. Keep bars chilled to maintain texture.
Freezer: You can freeze unfrosted bars for up to 3 months. Wrap each bar in plastic wrap and place in a freezer bag. Thaw in the refrigerator overnight. Texture may soften slightly after freezing.
Reheating: Serve chilled or rewarm at 120°C (250°F) for 8–10 minutes to take the chill off; avoid microwaving, which makes the crust soggy.

Variations & Substitutions

Gluten-Free Version: Replace 250 g (2 cups) all-purpose flour with a 1:1 GF blend and add 1/2 tsp xanthan gum. Bake crust 1–2 minutes longer. Texture will be slightly crumbly.
Lighter Custard: Use 600 ml (2.5 cups) whole milk and omit the heavy cream; custard will be lighter but less glossy. Keep cornstarch the same.
Eggless Version: Whisk 45 g (4 tbsp) cornstarch with 150 g (3/4 cup) sugar, and heat with 720 ml (3 cups) milk and 120 ml (1/2 cup) cream until thickened. Add vanilla. This yields a set, but slightly different mouthfeel.
Berry Mix: Replace half the rhubarb with strawberries or raspberries (same weight). No timing change, but watch for extra juice; lightly macerate and drain.
Caramel Rhubarb: Sprinkle 2 tbsp light brown sugar over rhubarb before assembling for a caramel note; the custard and baking time remain the same.

Serving Suggestions & Pairings

Serve with a spoonful of lightly sweetened whipped cream and a dusting of lemon zest.
Pair with a small scoop of vanilla bean ice cream and a hot cup of espresso for contrast.
For a brunch spread, include tangy fruit bars like these alongside scones and magic cookie bars for variety.
A crisp late-harvest Riesling or a dry Prosecco complements the tart rhubarb and creamy custard.

Nutrition Information

Per serving (1 bar). Yield: 9 bars; Serving size: 1 bar.

Calories: 320 kcal
Total Fat: 18 g
Saturated Fat: 10 g
Cholesterol: 110 mg
Sodium: 180 mg
Total Carbohydrates: 36 g
Dietary Fiber: 1.5 g
Sugars: 20 g
Protein: 5 g

Nutrition values are estimates. Actual values may vary based on specific ingredients and preparation methods.

Frequently Asked Questions

Q: Why did my custard turn out watery or not set?
A: The most common cause is excess liquid from the rhubarb or undercooked custard. Pre-cook and drain the rhubarb, and cook the custard until it thickly coats a spoon (about 4–6 minutes) before pouring.

Q: Can I make this without eggs?
A: Yes. Use a cornstarch-thickened custard (see Variations). The set will be slightly different — more pudding-like — but still delicious.

Q: Can I double this recipe?
A: Yes. Use two 9 x 13-inch pans or one very large pan and adjust baking time slightly. If using a deeper pan, bake until the center barely jiggles. Cooling and chilling times remain the same.

Q: Can I prepare this the night before?
A: Absolutely. In fact, chilling overnight improves slicing and flavor. Assemble and chill for at least 2 hours or overnight before slicing.

Q: How long does this keep in the fridge?
A: Stored in an airtight container, these bars keep well for up to 4 days in the refrigerator.

Q: Can I use frozen rhubarb?
A: You can, but thaw and drain it thoroughly, then cook briefly to remove excess moisture before adding to the crust.

Q: My crust is too hard — what happened?
A: Overworking the dough or using too much butter can make a dense crust. Work just until the mixture holds together and press it gently into the pan.

Conclusion

If you want a slightly different take, this riff on the bars from The Baked Collective is a helpful comparison for technique. For another tested home-baker version with useful troubleshooting notes, see the recipe by Chef Heidi Fink.

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