Preheat the oven to 325-degrees. Spray or grease and flour 2 large loaf pans (9”x5”). You can additionally line the pans with a sheet of parchment paper making it easy to remove the cakes if desired.
Pour about 4 cups of warm water into a large pan (I use a metal baking pan, 9”x13”). Place the pan with water on the very top rack of the oven. Place the other rack on the second lowest position in the oven for the cakes.
Combine the butter and the shortening in a large mixing bowl. Beat together on medium speed for 3 minutes then add the sugar, beating until light and fluffy.
Add eggs one at a time, blending into the butter mixture on medium speed, scraping down the sides and bottom of the bowl as needed.
In a separate bowl whisk together the flour, kosher salt, baking powder and cocoa powder.
Blend the flour in on low speed, about ½ cup at a time alternating with the buttermilk, beginning and ending with flour.
Stir in the vanilla and chocolate extracts on low speed.
Add the chopped semisweet chocolate and continue blending in on low speed just until the chopped chocolate is mixed into the batter.
Divide the batter between the prepared loaf pans. Place the loaf pans on the second lowest rack in the oven and bake for 40 minutes then carefully remove the pan of water.
Continue baking the cakes for an additional 20 minutes or until the pound cakes test done when a toothpick is inserted in the center.
Cool the cakes in the pans on a rack for 15 minutes then remove them and cool completely on a wire rack.