Preheat the waffle iron according to the manufactures directions. If you are using frozen blueberries, defrost them on paper towels to absorb the excess moisture before using.
In a large bowl, whisk together the flour, salt, baking powder and sugar.
In a large capacity measuring cup, beat the eggs, then stir in the milk, butter and vanilla.
Pour the milk mixture into the flour mixture; then beat until mixed completely. Stir in the blueberries.
Spray the waffle iron with a non stick spray.
Ladle the batter (making sure you get some blueberries in there as they may sink to the bottom) into a preheated waffle iron and close the lid.
Cook the waffles until they are golden brown and crisp.
Serve with a few extra berries on top, syrup, whipped cream etc.
Notes
The waffle iron may need to be sprayed with non stick spray between waffle batches as the blueberries make it a bit sticky!