Preheat oven to 350°F. Grease your donut pans with oil or butter.
In a mixing bowl, stir together the flour, sugar, salt, and baking powder.
Make a well in the center of the dry ingredients, and add your milk, butter, and egg.
Mix well to create a batter.
Using a food processor or immersion blender, puree your berries.
Add the berries to the batter and stir to combine.
Transfer your batter to a piping bag, then pipe into the donut pan, filling each donut about half way full.
Bake for 8-9 minutes.
Let cool in the pan for about 3 minutes, then remove and finish cooling on a cooling rack.
Make the glaze by mixing the milk, powdered sugar, and salt, adjusting for consistency.
Dip the donuts one at a time, then return to the cooling rack to allow excess to drip away. Enjoy!