• Preheat the oven to 350ºF (177ºC).
• Spray an 8" square baking pan with non-stick spray. Set aside.

STREUSEL TOPPING

• Place flour, brown sugar, cinnamon, and salt into a small bowl. Toss together with a fork until combined.
  ¼ cup (30g) all-purpose flour, 2 Tablespoons (25g) firmly packed light brown sugar, ¾ teaspoon ground cinnamon, ⅛ teaspoon salt
• Add the butter to the bowl, then use a fork to smash the pieces of butter into the mixture.
  2 Tablespoons (28g) unsalted butter
• Use your fingers to press the ingredients together until butter is in small chunks. I like to pick up chunks of butter and gently pinch them between my thumb and pointer and middle fingers to flatten slightly. I then drop the flattened pieces of butter back into the mixture so they pick up the dry mixture, then go through the whole bowl again with all of my fingers to "fluff" the mixture and turn the flattened pieces back into larger chunks. You are aiming for mostly medium-size chunks and some smaller and larger chunks. Set aside.

COFFEE CAKE

• In a medium size bowl, toss together the flour, cinnamon, baking powder, baking soda, and salt. Set aside.
  1 and ¼ cups (150g) all-purpose flour, ½ teaspoon ground cinnamon, 1 teaspoon baking powder, ¼ teaspoon baking soda, ¼ teaspoon salt
• In a large bowl with a handheld mixer or the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugars until light and fluffy. Add the egg, then beat on medium speed until combined. Add the vanilla and the sour cream and beat again on medium speed until completely incorporated.
  6 Tablespoons (85g) unsalted butter, ½ cup (100g) firmly packed light brown sugar, ¼ cup (50g) granulated sugar, 1 large egg, 1 teaspoon vanilla extract, 3 ounces (85g) full fat sour cream
• Stop the mixer and fold in the dry ingredients gently with a spatula until no flour lumps remain. Do not over mix batter.
• Spread the coffee cake batter in the prepared pan, then top with blueberries, spacing them out evenly over the top of the batter. Sprinkle the streusel evenly on top of the blueberries, then bake for 32-36 minutes, or until a toothpick or cake tester inserted in the center comes out mostly clean.
  6 ounces fresh blueberries2
• Remove from oven and allow to cool completely on a wire cooling rack. Enjoy as is, dust with powdered sugar, or mix ½ cup powdered sugar with 1-2 Tablespoons of water or milk to make a simple glaze. Leftovers can be kept covered tightly at room temperature up to 5 days or in the refrigerator up to one week. Coffee cake freezes well, up to 2 months. Thaw in fridge overnight and allow to come to room temperature.