Pre-heat oven to 350 °F (180 °C). Butter a 9 x 9-inch (18 x 18 cm) pan, lined with greased paper on the bottom.
Melt butter and chocolate over hot, not boiling water. Remove chocolate from heat and cool it for 5 minutes. Stir in sugar, salt and vanilla. Add eggs, one at a time, mixing well after each addition. Add flour and cocoa, gradually, stirring until all ingredients are incorporated and mixture is smooth.
Transfer batter to prepared pan and bake in oven for 40 to 45 minutes. Remove from oven and run a knife around inside edge. Invert pan onto a flat surface and peel of paper. Turn again onto the rack and cool completely. Cut in 2-inch (4 cm) squares and sift confectioners sugar on top.
Yields: 16 brownies