Preheat oven to 350 F.
Line an 8 x 8 inch baking pan with parchment paper - two strips that are 8 inches wide and long enough to hang over the sides by several inches. Place in opposite directions in the baking pan. This will ease the removal of the brownies once baked without damaging their tops.
Fill a small saucepan a quarter of the way full with water and place over low heat. Bring to a simmer. Place dark chopped chocolate and butter in a medium s/s bowl and place over double boiler. Melt chocolate and butter, stirring occasionally. Once the chocolate and butter have melted, remove from heat and let cool.
Sift flour, cocoa, and salt together into a medium bowl and set aside.
Combine melted chocolate with sugar and beat until blended. Add eggs, one at a time, blending after each addition. Add vanilla. Blend in the flour mixture and fold in the chopped white chocolate.
Bake in oven for 30 to 40 minutes until the edges are just starting to come away from the side of the baking pan. The top of the brownie should be shiny and have a paper like crust. Remove from oven and let cool completely in the pan, at room temperature. To remove brownie from pan, take hold of the parchment paper ends and lift brownie out of pan. Cut and serve.