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Whole Wheat Jammy Berry Crumble Bars

3 bars stacked on top of one another with a glass of milk and berries on the side

These Whole Wheat Jammy Berry Crumble Bars are tart, buttery, and reminiscent of a soft-baked Nutri-Grain bar. They are bursting with blueberries and strawberries and are the perfect jumpstart to summer, whether the fruit is in season or not. Use fresh or frozen berries!

Ingredients

Scale

For the crust and topping:

  • 1 1/4 cups plus 2 Tablespoons (180g) whole wheat flour*
  • 1/2 cup (50g) old-fashioned rolled oats
  • 1/4 cup (50g) white granulated sugar
  • 1/4 cup (50g) brown sugar
  • 1/4 teaspoon baking soda
  • 1/4 teaspoon salt
  • 1/2 teaspoon ground cinnamon
  • 1/2 cup (113g) unsalted butter, at room temperature, sliced into 1/2-inch thick cubes*
  • 1 egg

For the jam:

  • 6 cups (1.5 lbs) frozen or fresh strawberries
  • 1 cup (150g) frozen or fresh blueberries
  • 1/4 cup (50g) granulated sugar (or more to taste)

Instructions

Prepare the crust: 

  1. Position a rack in the middle of the oven and preheat the oven to 350°F (180°C). Butter an 8×8 inch baking pan and line with parchment paper. 
  2. Using a stand mixer: In the bowl of a stand mixer fitted with a paddle attachment, mix the flour, oats, granulated and brown sugars, baking soda, salt, and cinnamon on medium-low speed to combine. Add the butter and mix until a dry, crumbly mixture forms, about 3 minutes. Add the egg and mix until the egg is fully incorporated and the mixture has a wet, coarse sand appearance, about 2 minutes.  By hand: In a large bowl, whisk together the flour, oats, granulated and brown sugars, baking soda, and salt. Add the butter, and using your hands or a pastry blender (affiliate link), break up the butter in the mixture until a dry, crumbly mixture forms, about 8 minutes. Add the egg, and mix using a wooden spoon until the egg is fully incorporated and the mixture has a wet, coarse sand appearance, about 2 minutes. 
  3. Reserve 1 cup plus 2 tablespoons (150g) of the flour mixture for the topping. Press the rest of the flour mixture into the bottom of the prepared pan. Bake for 10 minutes. Prepare the jam while the crust is baking.
  4. After 10 minutes, remove the pan from the oven and let it cool to room temperature on a baking rack. 

Prepare the jam:

  1. In a 2.5- to 3.5-quart saucepan (the wider the better), combine the strawberries, blueberries, and sugar. Set the pan over medium heat and bring the mixture to a bubbly simmer. Cook, frequently stirring, until the fruit breaks down, the jam thickens, and any excess liquid evaporates about 20 minutes. Let the jam cool to room temperature. You should have about 1 1/4 cups of cooled jam. 

To assemble the crumble bars:

  1. Once the crust and jam are cooled, spread the jam over the crust. Leave a 1/4-inch border around the edge of the pan. Sprinkle the remaining crust over the jam and press down lightly onto the crumble using the palms of your hand. Bake until the top is golden and crisp, about 45 minutes.
  2. Let the crumble cool completely in the pan set on a wire rack. Once cooled, remove the crumble using the parchment paper sling. To get the cleanest cuts, place the cooled crumble in the refrigerator or freezer and chill before cutting. 

Equipment

Notes

Adapted from Sarah Kieffer’s Blueberry Crumble Bars with Apple and Shauna Sever’s Jammy Winter Fruit and Browned Butter Bars

DOUBLING IT? Use a 9×13″ baking pan and increase the crust baking time to 20 minutes, and the crumble baking time to about 65 minutes. You can also use two 8×8-inch pans to reduce the total baking time.

WHOLE WHEAT FLOUR. If you opt to measure by volume instead of weight, whisk the flour first to aerate it, then spoon into a measuring cup, and then level it off with the back of a knife. 

BUTTER. I used room temperature butter that is 65°F (18°C). If you don’t have a thermometer, test the butter by placing your finger on the butter and pressing down slightly. Room temperature butter will be cool to the touch and leave a slight indentation.

DO AHEAD. The jam freezes wonderfully and can be used for so many purposes so it’s worth doubling. To freeze, cool the jam to room temperature and place it in a freezer zip-lock bag. Spread the jam evenly in the bag so it lays flat. Seal the bag, making sure there are no air pockets in the bag. Place the bag flat in the freezer. Alternatively, freeze the jam in a freezer-safe, air-tight container with a lid, such as a glass food storage container (affiliate link). Defrost in the refrigerator or reheat in a 2.5- 3.5 quart saucepan over medium-low heat. Keep frozen up to 3 months. 

STORAGE. Store in an airtight container for four days in the refrigerator. You can also store these bars in the freezer in an airtight container or plastic freezer bag. Let the bars defrost at room temperature before eating, about 60 minutes. 

Nutrition

Keywords: strawberry crumble bars, blueberry crumble bars, berry crumble bars