In a small bowl, pour boiling water over the chocolate
Set aside to melt and cool for about 20 minutes.
Grease and flour a 9x5x3-inch loaf pan.
Preheat oven to 325°.
Sift flour into a bowl with salt and baking soda.
In a large mixing bowl with an electric hand-held mixer at high speed, cream butter and brown sugar
Add eggs and vanilla and beat until light and fluffy.
On low speed, beat in flour mixture, alternating with sour cream, ending with flour mixture.
Beat in chocolate mixture until just blended.
Pour batter into prepared loaf pan.
Bake chocolate pound cake for about 1 hour, or until a wooden pick or cake tester comes out clean.
Cool in pan on rack for 15 minutes.
Remove from pan and continue cooling on rack.
Sprinkle cooled cake with sifted confectioners's sugar or drizzle with icing or glaze.