Blu-barb Crumb Bars with Oatmeal Streussel
Blueberry & Rhubarb Crumb Bars with Oat Streussel on a blue and yellow plate.
The Portable Cousin of Pie
As much as I love a good pie, sometimes bars are the better answer. They're easier to transport, easier to serve a crowd, and just as satisfying. These Blu-Barb Bars combine tart rhubarb and sweet blueberries beneath a buttery oat streusel with hints of ginger and cardamom.
The press-in crust makes this recipe especially approachable, and if you happen to own a quarter-sheet pan extender, it's worth pulling it out here. It helps create perfectly straight edges and makes cutting bakery-worthy bars much easier.
As with all of our fruit desserts, we'll whisk the sugar and starch together before tossing with the fruit. This ensures even distribution and a beautifully set filling.
Ingredients
Press-In Crust (9 x 13-inch Pan)
1 cup + 2 tablespoons (100 g) all-purpose flour
⅓ cup (42 g) spelt flour (or substitute all-purpose flour)
½ cup (99 g) granulated sugar
½ teaspoon (3 g) salt
½ cup (113 g) cold unsalted butter, cubed
1 tablespoon (15 g) heavy cream
Blueberry Rhubarb Filling
2 cups (225 g) rhubarb, sliced into ½-inch pieces
1 cup (225 g) blueberries
⅓ cup + 1 tablespoon (75 g) granulated sugar
2 tablespoons + 1 teaspoon (20 g) tapioca starch
Pinch of salt
½ tablespoon (8 g) fresh orange juice
Oat Streusel Topping
⅔ cup (160 g) rolled oats
⅔ cup (160 g) all-purpose flour
⅔ cup (200 g) raw sugar
½ teaspoon (3 g) salt
½ teaspoon ground ginger
½ teaspoon ground cardamom
⅔ cup (160 g) cold unsalted butter, cubed
Method
Preheat the oven to 300°F (150°C).
Grease a 9 x 13-inch baking pan and line with parchment paper if desired.
Make the Press-In Crust
In a mixing bowl, whisk together the all-purpose flour, spelt flour, sugar, and salt.
Cut the cold butter into the flour mixture until it resembles moist crumbs. Add the heavy cream and mix until absorbed. The mixture will remain crumbly.
Press firmly into the bottom of the prepared pan in an even layer.
Bake for about 15 minutes, just until the crust begins to look dry and lightly set.
Prepare the Filling
In a medium bowl, whisk together the sugar, tapioca starch, and salt until evenly combined.
Add the rhubarb, blueberries, and orange juice. Toss thoroughly to coat the fruit.
Set aside while preparing the streusel.
Make the Oat Streusel
In the bowl of a mixer, combine the rolled oats, flour, raw sugar, salt, ginger, and cardamom.
Add the cold butter and paddle on low speed until the mixture is crumbly but hydrated. The streusel should hold together when squeezed lightly in your hand.
Assemble and Bake
Spread the fruit mixture evenly over the partially baked crust.
Scatter the oat streusel generously over the fruit.
Bake at 350°F (175°C) for 45–55 minutes, or until the filling is bubbling around the edges and the streusel is golden brown.
Allow the bars to cool completely before slicing. For the cleanest cuts, chill the bars before portioning.
Storage
Store covered at room temperature for up to 2 days or refrigerate for up to 5 days.
Baker's Note
The combination of ginger and cardamom in the streusel plays beautifully with both blueberries and rhubarb, adding warmth without overwhelming the fruit. These bars are wonderful on their own, but a scoop of vanilla ice cream never hurts.
