Preheat oven to 350, or 325 for a non-stick pan.
Spray a 12 inch pizza pan with non-stick spray.
In a medium size saucepan melt butter, sugar, and unsweetened chocolate over low heat, stirring frequently, until all melted and smooth.
Add in vanilla and stir to mix.
In a large mixing bowl combine flour and salt.
Pour chocolate mixture in with the flour and thoroughly mix.
Add in eggs and mix until well incorporated.
Pour mixture in prepared pan and spread evenly.
Bake for 15 minutes, or until a toothpick inserted into the middle comes out clean. This is a very thin brownie so don’t overbake!
Remove from oven and place on a wire rack to cool completely.