Sift together sugar, flour, salt, and baking powder. Melt the square of chocolate and butter together. Blend in the milk and vanilla slowly. Mix together with dry ingredients. Pour into lightly greased pan; either 9" spring form or square (10"x10") works well. In separate bowl, combine the brown sugar, white sugar, and cocoa and sprinkle over top of batter. Pour the coffee over top of all. Bake at 350 degrees for 40 minutes. When done, turn out onto a tray or plate thats deep to reserve the fudge sauce that will form.