Preheat oven to 350 F.
In a large mixing bowl combine butter and sugars. Beat on low with an electric hand mixer or stand mixer until smooth and creamy. Add egg and vanilla. Mix on low until combined and then set aside.
In a separate large bowl, combine sifted flour and baking soda, salt. Whisk to combine and add to wet ingredients gradually. Add 1 cup at a time, beat on low until combined, and then continue with the next batch.
Mix until ingredients are almost combined with little to no lumps.
Stir in chocolate chips and then very gently mix in the blueberries. If the batter is too sticky, refrigerate it for 15-20 additional minutes. Scoop 2 tablespoonfuls of dough, rolling it into about 2 inch balls.
Arrange the cookie balls on a baking sheet lined with parchment paper at least 2 inches apart. Don’t press down! Bake for 10-12 minutes (the time varies due to different ovens).
The cookies will have a soft center inside. Once they cool down they will set well and the texture inside remains soft and buttery.
Let the cookies stand in the pan for 5-10 minutes before transferring to a wire rack (line a sheet parchment paper or foil underneath to catch the glaze drippings later).
Glaze. In a small mixing bowl smash the blueberries until smooth, carefully strain the juice out into a separate bowl. Add powdered sugar and whisk until combined.
The texture should be thick, but thin enough to pour. You can test on one cookie first and see how it sets, if it doesn’t have enough color add more sugar and/or food coloring. Drizzle the cookies with purple glaze using a fork or teaspoon. Let cool completely before serving. Enjoy!