The best lemon bars strike a perfect balance: They’re both sweet and tangy, their sharp, creamy centers anchored by a crisp, buttery crust. My desert-island dessert, they’re the one confection I can imagine eating ad infinitum – or, at least until the rescue plane arrives.
Because maintaining that sweet-tart balance is so essential, lemon bars aren’t the kind of loosey-goosey recipe that can take a lot of variation and still turn out well (chocolate chip cookies, I’m looking at you). As much as lemon-friendly ingredients like berries, herbs and almonds beckon, adding them can potentially throw things off-kilter, unless it’s done in a skilled and considered way.
And that is why I waited so long to bake something that seems so obvious in retrospect: lemon-blueberry bars.
Adding lemon to any blueberry dessert is a classic and arguably essential move; the acidity of the citrus brightens the sweet berries, making lively what can sometimes be dull.
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It doesn’t necessarily work in reverse. Most lemon-focused desserts want to stay that way, guarding the fierce tartness of the citrus. In this case, I wanted the blueberries to function like vermouth in a martini – a delicate enhancement that never overwhelms the gin’s punch.
The key was to make sure that these bars remained firmly in the citrus camp. I wanted lemon bars dotted with blueberries, not blueberry bars brightened with lemon.
The biggest challenge was in countering the berries’ sweetness. Cutting the sugar and increasing the lemon juice in the curd helped. But so did adding more lemon zest, which, while not acidic like the juice, intensified the lemon flavor and kept the berries in check. I also threw in a little lime zest to round out the citrus notes. But that’s purely optional.
Since the blueberries in the filling also add moisture, these are soft, puddinglike bars that can ooze a bit when warm. So store them in the refrigerator until just before serving.
For fancier occasions, these bars hold their own served on a plate with a fork, like a mini lemon tart. But even when they’re slightly warm and gooey, I still like to eat them out of hand. After all, you may not find cutlery on a desert island, but palm fronds make good napkins in a pinch.
Yield: 16 servings
Total time: 1 1 / 2hours, plus cooling and chilling
For the crust
1 1/4 cups all-purpose flour
1/3 cup confectioners’ sugar, plus more for dusting
1 teaspoon finely grated lemon zest
1/4 teaspoon fine sea salt
10 tablespoons/140 grams cold unsalted butter, cubed
For the curd
1 1/2 cups granulated sugar
3/4 cup fresh lemon juice (from 4 to 8 lemons)
3 large egg yolks
2 large eggs
2 teaspoons cornstarch
Pinch of fine sea salt
8 tablespoons unsalted butter (1 stick), diced
1/2 tablespoon finely grated lemon zest
1 1/2 teaspoons finely grated lime zest (optional or substitute lemon zest)
3/4 cup fresh blueberries
Heat oven to 325 degrees and line a 9-inch square baking dish with parchment paper so it hangs over the edges on all sides by a few inches. (You may need to use two pieces of parchment.)
In the bowl of a food processor, pulse to combine the flour, confectioners’ sugar, lemon zest and salt. Add butter and pulse until a crumbly dough forms, about 10 seconds. (Or mix dry ingredients in a bowl and use pastry cutter to cut in butter, clumping the mixture together in your hands until it holds together.) Press dough into prepared pan. Bake until light golden, 25 to 35 minutes.
As crust bakes, make the curd: In a medium pot, whisk together the granulated sugar, lemon juice, egg yolks, whole eggs, cornstarch and fine sea salt until well combined. Place over medium heat and stir with a heatproof rubber spatula (or wooden spoon), making sure to scrape around the sides and edges of the pot, until mixture is simmering and thickened, 5 to 10 minutes.
Bring mixture to a boil and let cook for about 30 seconds, but no longer than 1 minute. Immediately strain through a fine mesh sieve into a bowl. Stir in butter, lemon zest and lime zest, and stir until butter melts. Stir in blueberries.
Pour mixture over crust, then stir to evenly distribute berries. Return to oven, and bake until blueberries begin to burst and curd starts to turn golden around the edges, 33 to 45 minutes. Transfer to a wire rack to cool to room temperature. Chill in the refrigerator until thoroughly cold before cutting, at least 3 hours. Dust lightly with confectioners’ sugar right before serving.