In a large bowl or the bowl of a stand mixer, combine the softened butter with both sugars and beat until smooth and fluffy, about 1 minute.
Add in the egg, pistachio butter, and vanilla. Beat together until creamy.
Add in the flour, making sure to spoon and level to measure, salt and baking soda. Mix together with a spatula.
Fold in the chocolate chips.
Let the dough sit out at room temperature for 1-2 hours. This allows the flavors to deepen and prevents the cookies from spreading too much.
After the hour is up - preheat the oven to 350. Scoop 2 tablespoons of dough per cookie and roll into a ball. Add to a sheet pan lined with parchment paper. Place no more than 8 on a cookie sheet at a time since they will spread. I had to bake mine on two separate baking sheets and baked them one at a time.
Bake for 11–15 minutes, until the edges are golden brown. The middles will look soft. They will harden up as they cool.
As soon as cookies are out of oven, sprinkle with additional chocolate chips and flaky sea salt (optional). Let cool for 10 minutes.