Ingredients:

  • ½ cup All-Purpose Flour (for streusel)
  • ½ cup Granulated Sugar (for streusel)
  • 1 tablespoon Ground Cinnamon (for streusel)
  • 4 tablespoons cold Unsalted Butter, cubed (for streusel)
  • 1 standard box Yellow or White Cake Mix (approx. 432g)
  • 3 Large Eggs
  • ½ cup Sour Cream or Full-Fat Plain Yogurt
  • ¼ cup Melted Unsalted Butter (additional)
  • ¾ cup Water or Milk (as directed on box)
  • 1 cup Confectioners’ Sugar (for optional glaze)
  • 2-3 tablespoons Milk or Heavy Cream (for optional glaze)
  • ½ teaspoon Vanilla Extract (for optional glaze)

Instructions:

  1. Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan, or line with parchment paper.
  2. Make the Streusel: In a medium bowl, whisk together the flour, sugar, and cinnamon for the filling. Cut in the cold, cubed butter using your fingertips or a pastry blender until the mixture resembles coarse crumbs. Set aside.
  3. Prepare Batter: In a large bowl, combine the cake mix, 3 eggs, sour cream, melted butter, and liquid (water/milk). Beat with an electric mixer on medium speed for 2 minutes until just combined and smooth. Do not overmix.
  4. Layer the Cake: Spoon half of the cake batter into the prepared pan and spread evenly. Sprinkle two-thirds (2/3) of the streusel mixture over this batter layer.
  5. Gently dollop the remaining batter over the streusel layer, spreading carefully. Scatter the remaining one-third (1/3) of the streusel evenly over the top.
  6. Bake for 35–45 minutes. The cake is done when a wooden skewer inserted near the centre comes out clean, and the top is golden brown.
  7. Let the cake cool in the pan on a wire rack for at least 30 minutes before slicing. If using, whisk the glaze ingredients until smooth and drizzle over the slightly warm or cooled cake.