Gently melt butter and chocolate together in a glass bowl in the microwave or over a pot of simmering water. In a separate bowl whisk together eggs, salt, sugars and vanilla.
Stir egg mixture into chocolate mixture, and then add flour. Stir just until combined. Cool mixture in refrigerator until you can work with batter.
Form cookies into dime sized balls and roll in powdered sugar. Transfer cookies to a parchment lined sheet tray. Bake for 5 minutes or fudgier cookies or up to 8 minutes for crunchier and cracked cookies. Allow to cool before serving.