Preheat oven to 350 degrees.

Prep a 9 x 13 inch cake pan with nonstick baking spray.

Add flour, baking powder, baking soda, and salt to a sifter sitting over a medium size bowl. Set aside.

Add butter and sugar to a large mixing bowl, Use an electric mixer to mix the butter and sugar together for 3-5 minutes. (It should be fluffy and a pale yellow color.

Slowly add one egg at a time, beating after each addition, to the butter/sugar mixture.

Mix in the sour cream and vanilla. Beat one more time to combine all of the ingredients.

Scrape the sides and bottom of the mixing bowl with a rubber spatula. Mix again to combine all of the cake ingredients.

Reduce the mixer speed to low. Slowly begin to add in the dry ingredients.

Alternate a portion of the dry ingredients with buttermilk. Beat after each addition.

Scrape down the sides and bottom of the bowl. Use a rubber spatula to add the chocolate chips.

Stir to blend them completely in the cake batter.

Bake at 350 degrees for 28-32 minutes. (At 28 minutes, insert a toothpick in the center of the cake, check to see if the cake is done.)

When completely baked, remove from the oven, and set on a wire rack to cool completely.

Sift powdered sugar, cocoa powder, and salt in a large bowl. Set aside.

Add the butter to a mixing bowl. Beat with an electric mixer for about 3 minutes.

Add small amounts of powdered sugar, cocoa powder, and salt to the butter.

Slowly add in the milk and vanilla with the mixer set on low.

Continue to mix until the icing is smooth. Set aside for a short time to slightly harden.

With an offset spatula spread the icing on top of the cake.

Enjoy!