Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until fluffy. Add the egg and vanilla extract, mixing until well combined.

Stir in the sourdough starter until everything is well combined and smooth in texture.

In another bowl, whisk together the all-purpose flour, baking soda, baking powder, and salt. Gradually add the dry mixture to your wet ingredients, mixing until just combined.

Gently fold the blueberries into the cookie dough, being careful not to smash them.

Using a cookie scoop or spoon, drop dollops of the dough onto your prepared baking sheet, leaving space between each cookie.

Bake for 12 to 15 minutes, or until the edges are lightly golden.

Remove from the oven and allow to cool completely on a wire rack.

In a medium bowl, beat the softened cream cheese until smooth. Gradually add powdered sugar and a teaspoon of vanilla extract, mixing until creamy and spreadable.

Once cooled, generously spread the cream cheese frosting over each cookie.

These cookies are best enjoyed fresh but can be stored in an airtight container for a few days.