Begin by blending your fresh or frozen blueberries in a blender until smooth. Set aside half of this puree and use the other half for the brownie batter.

Transfer the remaining blueberry puree to a small saucepan and simmer over medium-low heat for 10-15 minutes until thickened slightly. Let it cool completely.

Preheat your oven to 325°F (163°C). Line an 8x8-inch baking dish with parchment paper.

In a mixing bowl, combine melted butter and sugar. Stir until well-blended, then add eggs, vanilla extract, and sea salt.

Fold the cooled blueberry reduction into the wet mixture gently.

Sift the flour into the wet mixture, mixing just until combined—about 30 seconds.

Pour the brownie batter into the prepared baking dish and bake for 35-40 minutes.

Allow the brownies to cool completely in the dish, about 30-45 minutes.

In a bowl, whisk together powdered sugar, milk, vanilla extract, and a pinch of salt until smooth. Spread the glaze over the cooled brownies.

Once the glaze has hardened, cut into 16 squares and store them in an airtight container.