Preheat oven to 350°F.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and sugar by mixing on medium speed until very light and fluffy, 5-8 minutes.
2 cups unsalted butter, 3 cups sugar
In a large measuring cup, whisk together the eggs, egg yolks, and vanilla. While the mixer is running on medium speed, very gradually pour the egg vanilla mixture into the butter sugar mixture in a steady stream. This process should take about about 1 minute - do not try to speed it up by pouring the entire mixture in at once. This gradual process helps keep the air that was incorporated into the butter and sugar without deflating it and creating a dry, dense cake.
6 large eggs, 6 large egg yolks, 1 tablespoon vanilla extract
After all the egg mixture has been incorporated, continue beating on medium speed 1 more minute.
Remove the bowl from the mixer stand. Use a sieve or sifter to sift 3 cups of flour and salt over the butter egg mixture in 3 additions, folding the mixture very gently with a rubber spatula after each addition.
3 cups all-purpose flour, 1 teaspoon salt
In a small bowl, add the chocolate chips and mix in 1 tablespoon of flour. This will help coat the chocolate chips and prevent them from sinking to the bottom of your cake during baking. Gently fold in the chocolate chips to the cake batter using a rubber spatula. Set batter aside while you grease the pan
2 cups semisweet chocolate chips, 1 tablespoon all-purpose flour
Using a pastry brush, liberally brush the shortening oil flour paste from step 1 all over the nooks and crannies of your bundt pan. Be sure to brush the center column and up the sides of the pan. Try not to let any mixture pool the bottom of the pan by brushing it up and out
Pour the batter into the prepared pan, making sure it is evenly distributed around the pan.
Bake in the preheated oven for 45-60 minutes or until a toothpick inserted in the center comes out clean.
Allow the cake to cool for 10 minutes then run a small offset spatula or butter knife around the sides of the tube pan and the center column. Place a grid wire rack over the cake and while holding the sides of the pan and wire rack together, flip the cake over onto the rack. Allow the cake to cool like this, without removing the pan, for about an hour. The pan should come off easily. If it does not, pour boiling water over top of a kitchen towel (do this in your sink) and place the steaming kitchen towel over top of the overturned bundt pan for 10 minutes. If this does not work, try placing the cake in the freezer until hard then turn the cake out onto a rack.
Dust with powdered sugar prior to serving, if desired
powdered sugar