1. Preheat oven to 350°F (175°C). Lightly grease a standard donut pan.
2. Mix dry ingredients: In a medium bowl, whisk together flour, baking powder, baking soda, and salt.
3. Mix wet ingredients: In a separate large bowl, whisk together sugar, eggs, milk, vanilla, and melted butter until smooth.
4. Combine mixtures: Add dry ingredients to wet and stir until just combined — do not overmix.
5. Fold in blueberries gently using a spatula.
6. Fill pan: Spoon or pipe the batter into the doughnut pan, filling each mold about ¾ full.
7. Bake for 15–18 minutes or until the tops are lightly golden and a toothpick inserted comes out clean.
8. Cool in pan for 5 minutes, then transfer to a wire rack to cool completely.

For the glaze

1. In a small bowl, whisk together powdered sugar, vanilla, and 1 tbsp milk until smooth.
2. Add more milk as needed, 1 tsp at a time, until glaze reaches your desired consistency.
3. Dip cooled doughnuts in glaze and set on a wire rack to dry.