Preheat the oven to 350° F. Line (2) cupcake pans with paper liners.
In the bowl of a stand mixer fitted with a paddle attachment, cream the butter, avocado oil, salt, and sugars on high speed until light and fluffy, approximately 2 minutes. Lower the speed to medium, add the eggs one at a time, then add the vanilla and mix well.
In a separate bowl, whisk together the buttermilk, sour cream, and espresso. In another bowl, sift together the flour, cocoa, and baking soda. At low speed, add the buttermilk mixture and the flour mixture alternately in thirds to the mixer bowl, beginning with the buttermilk mixture and ending with the flour mixture.
Mix only until just blended. Next, add the chocolate chips and fold the batter with a rubber spatula to be sure it’s completely blended.
Divide the batter among the cupcake pans (one rounded standard ice cream scoop per cup). Bake in the middle of the oven for 25 minutes until a toothpick comes out clean. Cool for 10 minutes, remove from the pans and allow to cool completely before frosting.