In a small bowl, mix together the milk and vinegar. Let sit for 5 minutes to "sour".
In a large bowl, mix together the flour, salt, baking powder and sugar.
When the milk has soured, beat in the egg, vanilla and butter. Add the wet ingredients to the dry ingredients, and mix until fully combined. Fold in the blueberries.
Allow the batter to rest for 30 minutes to 1 hour.
Heat a large skillet over medium heat and spray with cooking spray. Scoop ¼ cup of batter for each pancake, and flip when bubbles are covering the surface of the pancake. Cook the other side until it is golden.