Preheat oven to 350°F (175°C). Grease a loaf pan.
Cream butter, granulated sugar, and brown sugar until light and fluffy.
Add eggs one at a time, beating well after each addition. Mix in vanilla extract.
Whisk together flour, cocoa powder, baking powder, baking soda, and salt.
Alternate adding dry ingredients and sour cream to the wet mixture, beginning and ending with dry ingredients. Mix until just combined.
Fold in chopped pecans and chocolate chips.
Pour batter into prepared pan and bake for 60–70 minutes, until a toothpick inserted comes out clean.
Cool in pan for 10 minutes, then transfer to a wire rack to cool completely.
Heat heavy cream until just simmering. Pour over chopped dark chocolate, let sit 5 minutes, then stir until smooth.
Pour ganache over cooled cake and garnish with extra pecans.
