Blueberry Buckle
Prep Time:20 mins | Bake Time:45-50 mins |
Total Time:1 hr 10 mins | Serves:9 |
Part coffee cake and part fruit dessert, a blueberry buckle is an old-fashioned American bake designed to make generous use of fresh summer berries. A soft cake batter is loaded with blueberries and covered with a buttery crumb topping before baking. As the cake rises around the fruit and the topping settles unevenly into the surface, it develops the wonderfully craggy appearance that gave the dessert its name: the top appears to “buckle.”
It’s an especially useful recipe during blueberry season, when berries are plentiful and at their sweetest, but it’s equally at home on a breakfast or brunch table as it is served for dessert. Cut it into generous squares and serve it simply as it is, or add softly whipped cream or a scoop of vanilla ice cream when serving it after dinner.
What Exactly Is a Buckle?
A buckle belongs to a wonderfully broad family of traditional American fruit desserts with names such as cobblers, crisps, grunts, slumps, and pandowdies. Unlike a cobbler, where fruit is generally topped with biscuit dough or batter, a buckle begins with a cake-like batter into which the fruit is incorporated.
As it bakes, the cake rises while the berries soften and release their juices. The crumb topping settles into the uneven surface, giving the finished cake its characteristic buckled appearance.
Choosing Blueberries
Look for berries that are firm, plump, and relatively uniform in color. Fresh blueberries naturally have a dusty-looking, silvery coating called bloom. This protective coating is normal and is actually a useful indication that the berries haven't been excessively handled.
Avoid washing blueberries until you're ready to use them. Excess moisture encourages berries to deteriorate more quickly during storage.
Fresh or Frozen Blueberries?
Fresh blueberries are wonderful when they're in season, but frozen berries can make blueberry buckle possible throughout the year.
If using frozen blueberries, don't thaw them first unless your particular recipe directs you to. Thawed berries release considerably more juice and are more likely to streak the batter. Fold frozen berries directly into the batter and be prepared for the cake to require a little additional baking time.
Dry the Berries Well
After rinsing fresh blueberries, spread them over a clean kitchen towel or paper towels and allow them to dry thoroughly before folding them into the batter.
Adding a significant amount of surface water can introduce unnecessary moisture to the cake, and dry berries are also easier to fold evenly through a thick batter.
Fold the Blueberries in Gently
Blueberries can burst when they're stirred too aggressively, leaving purple streaks throughout the batter. Once the cake batter is mixed, use a flexible spatula to fold in the berries with as few strokes as possible.
A few broken berries won't hurt anything, but gentle handling gives the finished cake a prettier crumb with distinct pockets of fruit.
Why Is the Batter So Thick?
Buckle batter is generally thicker than the batter for an ordinary layer cake. That structure is useful because it helps suspend a generous quantity of fruit rather than allowing all of the berries to immediately sink toward the bottom.
Resist the temptation to thin the batter simply because it seems unusually thick. Once the berries begin releasing their juices in the oven, they'll contribute additional moisture to the cake.
How to Tell When a Fruit-Heavy Cake Is Done
Testing a blueberry buckle can be slightly trickier than testing a plain cake because inserting a toothpick directly into a berry can make it appear as though the batter is still wet.
Test in two or three places near the center, looking for an area of cake rather than an obvious blueberry. The tester should emerge without wet batter, although a few moist crumbs are perfectly fine. The center should also feel set and spring back lightly when touched.
Let the Buckle Cool Before Cutting
Fresh from the oven, the fruit juices are still very hot and the cake's structure hasn't completely set. Give the buckle time to cool before cutting it into squares. It can certainly be served slightly warm, but allowing it to rest first produces cleaner slices and helps keep the berry-filled crumb intact.
Buckle Isn't Just for Blueberries
Once you understand the basic formula, a buckle is a wonderful way to make use of other seasonal fruit. Raspberries, blackberries, chopped peaches, plums, or combinations of berries can all inspire variations.
Because different fruits contain different amounts of moisture, however, substitutions aren't always perfectly one-to-one. Particularly juicy fruit may require adjustments to keep the cake from becoming overly wet.
Ingredients
Blueberry Cake
• 1¾ cups (210 g) all-purpose flour
• 1½ teaspoons baking powder
• ½ teaspoon kosher salt
• ½ cup (113 g) unsalted butter, softened
• ¾ cup (150 g) granulated sugar
• 2 large eggs, room temperature
• 2 teaspoons pure vanilla extract
• ½ cup (120 g) sour cream, room temperature
• ¼ cup (60 ml) whole milk
• 2 cups (300 g) fresh blueberries
• 1 tablespoon all-purpose flour, for tossing with the blueberries
Crumble Topping
• ¾ cup (90 g) all-purpose flour
• ½ cup (100 g) packed light brown sugar
• 1 teaspoon ground cinnamon
• ¼ teaspoon kosher salt
• 5 tablespoons (70 g) unsalted butter, melted and slightly cooled
Instructions
Preheat the oven to 350°F (175°C). Butter an 8-inch square baking pan and line with parchment paper, leaving a slight overhang on two sides.
In a medium bowl, whisk together the flour, baking powder, and salt.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and sugar on medium speed for 2 to 3 minutes, until pale and fluffy. Add the eggs one at a time, beating well after each addition, then mix in the vanilla.
Add the sour cream and mix just until combined. With the mixer on low, add the flour mixture in two additions, alternating with the milk. Mix just until the batter comes together.
Toss the blueberries with 1 tablespoon flour, then gently fold them into the batter with a rubber spatula.
Spread the batter evenly in the prepared pan.
For the crumble topping, combine the flour, brown sugar, cinnamon, and salt in a small bowl. Pour in the melted butter and stir with a fork until large, moist crumbs form.
Scatter the crumble evenly over the batter, gently breaking up any very large pieces with your fingers.
Bake for 45 to 50 minutes, until the topping is golden brown and a toothpick inserted into the center comes out clean or with a few moist crumbs. If you hit a blueberry, test again in another spot.
Let cool in the pan for at least 20 minutes before slicing and serving.
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