Preheat donut machine or preheat oven to 350 degrees.
In large bowl- combine flour, sugar & baking powder.- Whisk.
Whisk in eggs, then yogurt, then butter.
Fold in mashed blueberries & their juice.
Transfer to pastry bag & pipe into donut wells or scoop in to full size donut pan.
Cook 6 minutes for mini-donuts or 10-12 for full size in the oven.
Remove & cool on wire rack & repeat the cooking process for remaining batter.