Prepare madeleine pan by buttering and flouring pan lightly
Preheat oven to 375 degrees
Beat eggs and sugar with mixer, add vanilla and salt
Mix in flour on low just until blended
Pour in butter in a steady stream while mixing on low
Scrape sides and be sure everything is well blended
Place 1 blueberry in the bottom of each well in the madeleine pan, then place two scant tablespoons of Batter (or 1 heaping tablespoon of batter) on top of each blueberry, then add two more blueberries on top of the batter
Bake 7-9 minutes or until golden and the cookie springs back when gently pressed
Allow cookies to cool in pan, then dust with powdered sugar