Blueberry Walnut Streusel Cake

This blueberry walnut streusel cake is made with fresh blueberries and topped with a crunchy walnut oat mixture. It’s a quick and easy summer snack cake! 

Blueberry Walnut Streusel Cake made with fresh blueberries topped with oat-walnut mixture

During the bountiful summer months, it’s common to load up on way too much produce. However, having too much fruit is never problem when you enjoy baking!

Too many nectarines? This nectarine frangipane tart is heavenly. Don’t know what to do with those excess plums? This almond plum cake is unbelievable. 

What to do with all those fresh blueberries sitting in the fridge? This blueberry walnut streusel is the answer!

Blueberry Walnut Streusel Cake made with fresh blueberries topped with oat-walnut mixture

Blueberry Walnut Streusel Cake

This cake is made with a very thick vanilla cake batter spiced with a touch of cinnamon.

The batter makes for one 8-inch cake pan. Since it’s a small amount of batter, I suggest using an electric hand mixer. Most stand mixers may be too large to effectively mix this batter.

Step by Step instructions on how to make Blueberry Walnut Streusel Cake made with fresh blueberries topped with oat-walnut mixture

Fresh blueberries vs frozen blueberries

This recipe works best with fresh blueberries. Fresh blueberries are more firm and plump. After baking, the blueberries will still be recognizable and quite full. 

Frozen blueberries will change the color of the baked cake. The blueberries will stain the cake a greenish-blue tint. 

When frozen, the water content in the blueberries freezes into ice. During baking, this ice will melt and leak into the batter. The resulting baked blueberries will lack structure and be a bit mushy.

Blueberry Walnut Streusel Cake made with fresh blueberries topped with oat-walnut mixture

Oat Walnut Streusel Topping

The blueberry cake is topped with a crunchy, butter oat walnut streusel. A mixture of walnuts, rolled oats, sugar, cinnamon, and butter make up the streusel.

Quickly pulsed together the ingredients in a food processor. Use as much or as little of the streusel as you’d like. (The photos in this post show use of all the streusel!)

The streusel can used to top your favorite muffins!   

Blueberry Walnut Streusel Cake made with fresh blueberries topped with oat-walnut mixture

Notes on serving cake:

This cake will be very fragile hot straight directly from the oven. Allow the cake to cool before slicing.

I suggest using a serrated knife to slice the cake. This will ensure the blueberries are cleanly cut, rather than mashed with a regular knife.

The blueberry cake may be reheated after slicing. However, I actually enjoyed the cake best chilled straight from the fridge with a warm cup of coffee. 

Because this cake contains moist fruit, store leftovers in an airtight container in the fridge. 

slice of Blueberry Walnut Streusel Cake made with fresh blueberries topped with oat-walnut mixture

Blueberry Walnut Streusel Cake

This blueberry walnut streusel cake is made with fresh blueberries and topped with a crunchy walnut oat mixture. It's a quick and easy summer snack cake! 

Yield: 8-inch cake

Course Breakfast, Dessert, Snack
Servings 10 slices
Author Maryanne Cabrera

Ingredients

Cake:

  • 3/4 cup (170 g) granulated sugar
  • 6 Tablespoons (86 g) unsalted butter, room temp, softened
  • 1 large egg room temp
  • 1 ¾ cup (198 g) cake flour
  • 1 teaspoon baking powder
  • 1/2 teaspoon baking soda
  • 1/2 teaspoon ground cinnamon
  • 1/2 teaspoon kosher salt
  • 1/4 cup milk, or any milk alternative
  • 2 cups (8 oz/227 g) fresh blueberries, rinsed clean, pat dry

Streusel Topping:

  • 1/2 cup (65 g) walnuts, lightly toasted
  • 6 Tablespoons dark brown sugar
  • 4 Tablespoons old fashioned rolled oats
  • 1/2 teaspoon ground cinnamon
  • 1/4 teaspoon kosher salt
  • 2 Tablespoon unsalted butter, cold, sliced into small cubes

Instructions

Cake:

  1. Preheat oven to 350°F. Butter 8-inch round cake pan and line with parchment paper. Set aside.

  2. In a large bowl, use an electric hand mixer to cream together sugar and butter. Add egg. Mix until smooth.

  3. In a separate bowl, whisk together cake flour, baking powder, baking soda, cinnamon, and salt.

  4. Alternate adding dry mixture and milk to batter, beginning and ending with dry mixture. Add ⅓ of flour mixture to mixing bowl. Mix together using a sturdy spatual. Add half of milk. Mix to combine. Repeat adding ⅓ flour, followed by remaining milk, and remaining flour. Mix until just combined.

  5. Fold in bluberries until well distributed. Transfer thick batter to prepared cake pan. Spread into an even layer.

Streusel:

  1. Place walnuts, brown sugar, rolled oats, cinnamon, and salt in a food processor. Quickly pulse 3 to 5 times until walnuts are coarsely chopped. Add cold cubed butter. Pulse another 3 to 5 times until mixture is crumbly.

  2. Sprinkle streusel over cake batter.

  3. Bake for 40-45 minutes until streusel topping is golden brown and toothpick inserted in center out cake comes out clean. Allow cake to cool in pan for 10 minutes. Unmold cake and allow to cool to room temperature on wire rack. Dust with powdered sugar before serving.

Recipe Notes

  • This cake will be very fragile hot straight directly from the oven. Allow the cake to cool before slicing. For best results, use a serrated knife to slice cake.
  • Once sliced, the blueberry cake may be reheated. Cake can also be enjoyed at room temperature or chilled. 
  • Since this cake contains moist fruit, store leftovers in an airtight container in the fridge. Cake will keep in the fridge for up to 4 days.  

Ingredient Notes:

  • For best results, use fresh blueberries. Frozen blueberries will stain the cake a greenish-blue tint.
  • Lightly toast walnuts before making streusel. Allow toasted walnuts to cool before mixing.
  • How to Toast Walnuts: Spread walnuts in single layer on a baking sheet. Toast in 350°F oven for 8-10 minutes until light golden. Check on walnuts after 5 minutes to ensure walnuts are not browning too fast. Allow walnuts to cool before use. 
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