In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and sugar at medium until pale and fluffy, about 4 minutes, stopping halfway to scrape the sides and bottom of the bowl.
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.
With the mixer on low speed gradually add the flour mixture alternately with the sour cream beginning and ending with the flour mixture. (Add 3/4 cup of the mini chocolate chips with the last bit of flour).
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.
Pour the cake batter into the prepared pan. Sprinkle the remaining 1/4 cup of mini chocolate chips on top of the cake batter. Bake for 45 to 50 minutes.
Sift together the powdered sugar, malted milk powder, and cocoa powder. Add the chocolate mixture, vanilla, and heavy cream to the sifted ingredients and whisk together until smooth.
The perfect make ahead dessert, it can easily be made a few days ahead and glazed whenever you are ready to serve. Making it perfect for any and all special occasions or backyard BBQ!!