Preheat oven to 350F. Cream butter and sugar, add eggs one at a time beating well after each addition. Stir in vanilla.
Combine flour and salt, stir into butter mixture. Stir in cooled melted chocolate. Pour into a greased 9 by 13 inch pan and bake for about 40 minutes, until a toothpick inserted comes out almost clean. Let cool if you can!!