Butter a square baking pan, line the bottom with parchment then butter the parchment.
Chop the chocolate, cut the butter into pieces and melt them together in a double boiler over simmering water. When both are melted, stir and remove from heat.
Sift together sugar and flour. Beat the eggs with the vanilla and a pinch of salt.
Gently whisk the sugar mixture into the melted chocolate, then whisk in eggs. Allow batter to rest for 30 minutes.
Preheat oven to 325*
Pour the batter into the prepared pan and bake for 40 to 45 minutes or more. The brownies are done when a toothpick comes out almost clean.
Let brownies cool before cutting. They can be refrigerated, resulting in a denser texture, and making cutting easier.