Preheat oven to 350°. Coat a 12- cup Bundt pan with cooking spray.

Mix cocoa and chopped chocolate in a heatproof bowl. Pour boiling water over chocolates and stir to melt. Let stand to cool (about 2-3 minutes).

Meanwhile, combine flour, salt, and baking soda. Cream butter, brown sugar, and vanilla until creamy. Add eggs to the butter mixture.

Fold the sour cream into the cooled chocolate mixture. Add the flour mixture and the sour cream chocolate mixture to the butter mixture and blend. Add chocolate chips and stir to incorporate.

Pour into the prepared pan and bake for 55 minutes or until an inserted toothpick comes out clean. Cool slightly before removing from pan. Sprinkle with powdered sugar and serve. May be served with whipped cream