Heat oven to 350 Degrees. Lightly grease a 13 x 9 x 2 inch pan. In a medium saucepan over low heat, melt butter. Stir in cocoa; blend until smooth. remove from heat and cool slightly. Add sugar, vanilla, salt, and eggs. Beat thoroughly. Add flour and baking powder. Stir in nuts and chocolate chips. Batter will be stiff. Spread it evenly in prepared pan. Bake for 30 minutes or until top is dry and and brownies just begin to pull away from sides of the pan. Sprinkle with powdered sugar. Cool and cut into 36 brownies.