Preheat the oven to 350 degrees F. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and sugar at medium speed for 1 minute. Increase speed to medium high and continue to beat until pale and fluffy, about 3 minutes, stopping halfway to scrape the sides and bottom of the bowl.
1 (227 g) cup Unsalted butter, 1 ¾ (350 g) cup Granulated sugar
With the mixer on medium speed, add the eggs, one at a time, beating well after each addition. Beat in vanilla extract with the last egg.
3 large Eggs , 1 tablespoon Vanilla extract
Heat the water in a small saucepan until simmering, set aside. Meanwhile, in a medium bowl, sift together the all purpose flour, cocoa powder, baking powder, baking soda, and espresso powder. Whisk in the kosher salt. Spray a 12 cup bundt pan with non stick baking spray. Using a fine pastry brush, spread the baking spray to coat the pan making sure to get into all the nooks and crannies. Set aside.
2 (250 g) cups All purpose flour , ¾ (64 g) cups Dutch process cocoa powder, 1 teaspoon Espresso powder, 1 ½ teaspoon Baking powder, ½ teaspoon Baking soda , ¾ cup Hot water , ¾ teaspoon Kosher salt
With the mixer on low speed gradually add the flour mixture alternately with the sour cream beginning and ending with the flour mixture. (Add ¾ cup of the mini chocolate chips with the last bit of flour). Beat until just combined after each addition, stopping to scrape the sides of the bowl.
1 (240 g) cup Sour cream , 1 cup Semi-sweet mini chocolate chips
With the mixer on low, slowly add the hot water mixing until just combined. Remove bowl from the stand mixer and with a rubber spatula, gently fold the batter scraping the sides and bottom of the bowl.
Pour the cake batter into the prepared pan. Place a kitchen towel on the counter and GENTLY tap the pan on top of the towel to release any air bubbles. Sprinkle the remaining ¼ cup of mini chocolate chips on top of the cake batter.
Bake for 45 to 50 minutes or until a toothpick or cake tester comes out with a few moist crumbs. Remove cake from oven and allow it to cool in the pan on a wire cooling rack for 15 minutes. Invert cake onto wire rack to cool completely.