Blueberry Sugar Cookies with Streusel are the perfect combination between a soft and fluffy muffin and a buttery chewy cookie. The cinnamon streusel topping is a MUST. Make them with fresh blueberries or follow the recipe notes for trying frozen berries. Note that these cookies are very soft and can be a little fragile.
Use a hand mixer on low speed to cream together butter, oil, and sugars until well combined. Turn the mixer up to medium and beat until lightened and fluffy, about 2 minutes.
Beat in egg and vanilla extract until just combined.
Sprinkle the flour, cornstarch, baking powder, and salt over the dough and use a large spatula to fold in until just combined. Add the blueberries and fold in until just combined.
Chill:
Chill dough in the fridge for two hours.
Bake:
When ready to bake, preheat oven to 350°F. Line two large baking sheets with parchment paper. Prepare streusel topping: Blend the streusel ingredients together (butter, flour, brown sugar, cinnamon) in a bowl with a fork until totally combined.
Divide dough into eight large equally sized balls (SEE NOTES), about 1/3 cup each (or, around 95-100g per cookie). Place the cookies 4” apart on a baking sheet and gently press down with a small flat-bottom glass or your fingers until each cookie is about 3/4” thick.
Sprinkle small pinches of the streusel evenly on top of each cookie. You'll use about 1 heaping tablespoon per cookie. Preparing both your cookie sheets of cookies at the same time helps adjust the amount easily between the cookies.
Bake cookies one tray at a time for about 16-18 minutes or until set and the edges are golden brown. We want the cookies to stay soft (so slightly underbaked). Let cool for 10 minutes then move to a cooling rack to cool for another 20-30 minutes.
Notes
Notes about the texture: As I noted earlier, the size of these cookies plus the fresh blueberries makes them soft and a little delicate. They are soft potentially-breakable “pick up with two hands” cookies.Make Them Smaller: I like dividing this recipe up into smaller cookies as well. Try about a 2 tablespoon scoop or so (about 20-24 cookies) and slightly flatten each scoop of dough on the tray. Bake for about 10-14 minutes and remove from oven when the edges are golden brown, but the centers are still a bit soft. Using Frozen Blueberries: You can use frozen blueberries and it actually works quite well! I suggest Wyman’s Wild Frozen Blueberries (I would use about 3/4 cup) because they are smaller than standard blueberries and work much better in the recipe.The dough WILL turn purple! The berries will also freeze the dough quite quickly, so using a cookie scoop is going to be easiest way to get these cookies onto the tray. Skip chilling the dough and make these cookies a little smaller (divide dough into 20-24 cookies).How to store: Store the cookies at room temperature in an air-tight container for 24 hours or in the fridge for up to three days. They are actually really good chilled in the fridge—the streusel topping is just *chef’s kiss*. Freeze if desired for 1 month.Streusel notes: For a more crumbly streusel, cut the butter down to 2 tablespoons. I tested both ways and preferred the more buttery version since it stuck to the cookies so well!