In a large mixing bowl, combine melted butter, granulated sugar, and dark brown sugar and stir to combine. Stream in the vanilla extract, eggs, buttermilk, and avocado oil and stir.
Sift in the all-purpose flour, Dutch-processed cocoa powder, baking powder, baking soda, and salt. Gently fold in the dry ingredients until just combined, then fold in the chocolate chips.
Grease a 9"x5" loaf pan with nonstick cooking spray, line with parchment paper, and then lightly grease the paper as well. Scoop the batter into the loaf pan and spread into an even layer. Use the spatula to score the length of the loaf down the middle. (Optional): sprinkle turbinado sugar overtop the entire loaf, then dot with more chocolate chips.
Bake on 350℉ for 45-50 minutes, or until a toothpick inserted in the center comes out with only a few wet crumbs. Allow to cool in the pan for 5-10 minutes, then remove and let cool completely on a wire rack before cutting into slices.
