Preheat the oven to 180°C or 350°F. Spray your doughnut pan with non-stick spray. Set aside.
In a large bowl, mix together the flour, sugar, baking powder and salt.
In a separate bowl, mix all the remaining wet ingredients – the milk, butter, vanilla and egg – until you have a creamy consistency.
Add the wet mixture to the dry mixture gently. Mix them together until everything is combined. Once ready fold in the blueberries gently.
Fill the doughnut pan with the blueberry batter, filling about halfway.
Bake the doughnuts for 10 minutes, until they're fully cooked from the inside and a cake tester comes out clean.
Allow them to cool for few minutes in the pan before placing them on a cooling rack. Let them cool completely.
For the glaze, in a small bowl, whisk together the icing sugar with 1 tbsp of juice (of your choice). Add an extra tbsp until you've achieved your desired consistency.
Dip the doughnuts in the glaze and place them back on the cooling rack, for the extra glaze to drip off. The doughnuts can be enjoyed immediately or after the glaze have set. Enjoy!