Ingredients:

  • 125g all-purpose flour
  • 150g dark brown sugar, packed
  • 2 tsp ground cinnamon
  • 113g unsalted butter, cold and cubed
  • 375g all-purpose flour
  • 200g granulated sugar
  • 1 tbsp baking powder
  • 1 tsp baking soda
  • 0.5 tsp fine sea salt
  • 225g full-fat sour cream, room temperature
  • 2 large eggs, room temperature
  • 113g unsalted butter, melted and slightly cooled
  • 2 tsp pure vanilla extract
  • 300g fresh or frozen blueberries
  • 120g powdered sugar
  • 2 tbsp whole milk
  • 0.5 tsp vanilla bean paste

Instructions:

  1. Preheat your oven to 350°F (175°C). Grease a 9x13-inch pan. In a medium bowl, combine 125g flour, dark brown sugar, and cinnamon. Work the 113g cold cubed butter in with a pastry cutter until the mixture looks like coarse sand. Set aside in the fridge.
  2. In a large bowl, whisk together 350g of the flour (reserving 2 tbsp), granulated sugar, baking powder, baking soda, and salt.
  3. In a separate container, whisk together the sour cream, eggs, melted butter, and vanilla extract until smooth.
  4. Toss the blueberries with the reserved 2 tablespoons of flour to prevent sinking. Fold the wet ingredients into the dry ingredients until just combined, then gently fold in the floured blueberries.
  5. Spread the batter evenly into the prepared 9x13 pan. Sprinkle the chilled streusel mixture over the top in an even layer.
  6. Bake for 45 minutes or until a toothpick inserted into the center comes out clean. While the cake cools, whisk together powdered sugar, milk, and vanilla paste for the optional glaze and drizzle over the top.