To make the streusel, cut the butter, flour, brown sugar, and cinnamon together in a small bowl until it forms small clumps.

Chill while you make the cookie dough.

To make the cookie dough, in the bowl of a stand mixer fitted with the paddle attachment, beat together the granulated sugar, brown sugar, butter, and lemon zest on medium speed for 3-4 minutes, or until light and fluffy.

Add the vanilla and egg and mix for 1-2 minutes, or until well combined.

Stir in the flour, baking powder and salt just until combined.

Fold in the blueberries just until incorporated.

Scoop out 2 tablespoons of cookie dough.

Gently press one side of the cookie dough into the streusel mixture.

Loosely cover and chill for 30 minutes.

Preheat the oven to 350°F and line two baking sheets with parchment paper or silicone baking mats.

Place the dough balls at least 3 inches apart on the prepared baking sheets.

Bake for 12-17 minutes, or until the edges are set and the streusel is golden brown.

Let the cookies cool on the baking sheet for 5 minutes, and then transfer to a wire rack to finish cooling.

To make the glaze, melt the butter in a medium microwave safe dish.

Whisk in the powdered sugar a little at a time.

Add enough cream to form a glaze that can be drizzled but is still on the thicker side.

Whisk in the vanilla extract.

Lightly drizzle the glaze over the cooled cookies.