Preheat oven to 350°F. Line a baking sheet with parchment and set aside.
In a large bowl, or the bowl of your stand mixer with paddle attached, add in butter, brown sugar and granulated sugar and beat on medium for about 3-4 minutes.
Add in your egg, and mix until combined. Make sure to scrape down the sides of your bowl to get the egg incorporated into all of the sugar mixture.
Add your vanilla and salt and mix in.
Add you black cocoa and mix well.
Add your dry ingredients, and mix on low until no dry flour remains. This dough will be very thick!
Dump in your butterscotch chips and stir to combine.
Using a ¼ cup/2 ounce scoop, scoop 5-6 cookies on your baking sheet, leaving ample room for cookies to spread.
Bake on the center rack of your oven for about 14 minutes. Remove from oven and sprinkle with flaky sea salt. Carefully transfer cookies to wire cooling rack, they will be very soft still but will firm up after cooling.
Store in an airtight container for up to a week, but cookies are best day of until about 2 days later. Enjoy!
