Preheat oven to 350F (175C) and line a baking sheet with parchment paper. Set aside and prepare streusel.

StreuselCut butter into pieces, place in a microwave-safe dish and heat in the microwave in 15 second intervals, stirring in between, until melted. Set aside to cool a bit.

In a medium-sized mixing bowl, whisk together flour, sugar, brown sugar, and salt.

Drizzle melted butter over the flour mixture and use a fork to toss and claw the ingredients together until you have a crumbly streusel. Set aside while you prepare the cookie dough.

Cookie DoughIn a large mixing bowl (or bowl of a stand mixer), combine butter, cream cheese, and sugars and use an electric mixer to beat until well-creamed, light, and fluffy (at least a minute on high speed).

Add egg and vanilla extract and stir until completely combined.

In a separate mixing bowl, whisk together flour, cornstarch, baking powder, and salt.

Gradually add the dry ingredients to the wet, stirring on low-speed until just combined.

Add blueberries and use a spatula to gently fold into the batter until well distributed.

Scoop dough by level 1 ½ Tablespoon sized scoop and drop on prepared baking sheet.

Grab a handful of streusel (about a heaping tablespoon) and press firmly onto the top of the cookie dollop. Scoop another level 1 ½ Tablespoon-sized scoop of dough and drop directly on top of the streusel. Portion out another handful of streusel and press gently but firmly on top of the dough to slightly flatten the cookie and to embed the streusel into the cookie.

Repeat with remaining cookie dough, spacing cookies at least 2” apart on baking sheet.

Bake in center rack of 350F (175C) oven for about 15 minutes and a toothpick inserted in the center of the cookie comes out clean or with moist crumbs. Allow to cool completely on baking sheet before drizzling with glaze.

GlazeCombine powdered sugar and 1 Tablespoon of milk and whisk until smooth. If too thick, add additional milk, a splash at a time, until smooth.

Drizzle glaze over cooled or mostly cooled cookies. Allow to solidify before serving.