Sift together the all-purpose flour, baking soda, and cocoa powder.
Beat together the softened butter, brown sugar, granulated sugar, eggs, and vanilla.
Beat in the sour cream.
Add the dry ingredient mixture into the wet ingredients and beat on low. Don't overmix.
Stir in the 1 cup of semisweet chocolate chips.
Pour half of the batter into one greased loaf pan and pour the remaining batter in the 2nd greased loaf pan. Top with extra chocolate chips if desired.
Bake in the preheated oven for about 55 minutes and check the center of the loaf with a toothpick to check for doneness.