Ingredients:

  • 1/2 cup (100g) unsalted butter, cold and cubed
  • 1 cup (120g) all-purpose flour
  • 1/2 cup (100g) granulated sugar
  • 1/4 cup (50g) packed light brown sugar
  • 1 tablespoon ground cinnamon
  • 1/4 teaspoon salt
  • 1 1/2 cups (180g) all-purpose flour
  • 1 teaspoon baking powder
  • 1/2 teaspoon baking soda
  • 1/4 teaspoon salt
  • 1/2 cup (113g) unsalted butter, softened
  • 3/4 cup (150g) granulated sugar
  • 2 large eggs
  • 1 teaspoon vanilla extract
  • 3/4 cup (180ml) sour cream, room temperature
  • 1 cup (120g) powdered sugar
  • 2-3 tablespoons milk or cream
  • 1/2 teaspoon vanilla extract (optional)

Instructions:

  1. Prepare the Streusel: Combine cold butter, flour, sugars, cinnamon, and salt in a bowl. Cut butter into the mixture using a pastry blender or your fingers until it resembles coarse crumbs. Set aside.
  2. Preheat and Prep: Preheat oven to 350°F (175°C). Grease and flour a 9-inch square baking pan, or line with parchment paper.
  3. Dry Ingredients: In a medium bowl, whisk together flour, baking powder, baking soda, and salt.
  4. Cream Butter and Sugar: In a large bowl, cream together softened butter and sugar until light and fluffy.
  5. Add Eggs and Vanilla: Beat in eggs one at a time, then stir in vanilla extract.
  6. Alternate Dry and Wet: Gradually add the dry ingredients to the wet ingredients, alternating with the sour cream, beginning and ending with the dry ingredients. Mix until just combined – don't overmix!
  7. Assemble and Bake: Pour batter into prepared pan. Sprinkle evenly with the streusel topping. Bake for 35-40 minutes, or until a toothpick inserted into the center comes out clean.
  8. Cool and Glaze (Optional): Let cool in the pan for 15-20 minutes before glazing (if using). To make the glaze, whisk together powdered sugar, milk/cream, and vanilla extract until smooth. Drizzle over the cooled coffee cake.