Preheat the oven 350 degrees F. Lightly spray 2 9-inch round cake pans with non-stick baking spray. Place parchment paper in the bottom of the pans then spray the top of the paper with more non-stick baking spray. Set aside.
In a medium-sized bowl, stir together the flour, baking powder, baking soda, and salt.
In another medium-sized bowl place the chocolate chips and add 1 ½ Tablespoons of the flour mixture and toss with the chocolate chips to make sure they are coated, set aside.
In the body of a stand mixer with the paddle attachment, beat the butter with the granulated sugar and brown sugar for 3 minutes.
Add the eggs one at a time until fully mixed in then stir in the vanilla.
Add in half of the dry ingredients and stir it in until combined.
Next, add half of the buttermilk, and stir until combined. Repeat with the remaining dry ingredients and buttermilk, scraping down the sides as needed.
Lastly, add the chocolate chips and stir until they are evenly distributed in the batter.
Divide the batter between the two cake pans. Take a spatula and smooth out the top, this will ensure the cakes bake evenly.
Place in the oven and bake for 22-28 minutes, until a toothpick inserted into the center comes out clean.
When cakes are done, remove from the oven and let them cool completely in the pan.
While the cakes are cooling, make the frosting.
In the body of a stand mixer with the paddle attachment or in a large bowl with an electric hand mixer add the butter and beat until smooth.
Add the powdered sugar a little at a time, mixing the first batch in completely before adding more, the mixture will be thick.
Next, add the salt, vanilla, and the milk, mix together until smooth. Once mixed in, turn the speed up to medium-high and beat for 3 minutes until light and fluffy.
Gently stir in the chocolate shavings until just mixed in, this helps to ensure they do not bread up.
To assemble the cake, take the cakes out of the pan and discard the parchment paper.
Trim the tops of the cake if there is any doming so they are even and flat.
Place one of the cake layers bottom side down onto your serving dish or cake plate. Add about 1 cup of the frosting and smooth it out to the sides.
Place the other cake layer, top side down, on to the frosting.
Take about another cup of frosting and lightly frost the entire cake, making a crumb coat. Place the cake in the refrigerator for at least 2 hours or up to overnight to set.
Take the remaining frosting and frost the outside of the cake. Add more mini chocolate chips as garnish if desired. Cut and serve.