Make sure you've baked your pie crust according to package/recipe instructions. Set it aside to cool. Preheat oven to 325 degrees.
In a microwave-safe bowl, add 2/3 cup of chocolate chips and unsalted butter. Microwave in 30-second increments until completely melted, stirring after each increment. Once melted, add instant espresso, vegetable oil, and cocoa powder. Mix until combined.
In a separate bowl fitted for your stand mixer, add eggs, brown sugar, vanilla, and salt. Beat them on medium with a paddle attachment until thick and creamy, about 2 minutes. Add chocolate mixture and beat together on low until combined. Add flour and beat just until combined.
Using a spatula, scrape the sides of the bowl and mix until everything is incorporated. Add 1/3 cup of remaining chocolate chips and stir. Pour into baked pie shell and smooth the top.
Bake in preheat oven for 30-35 minutes, or until toothpick comes out with a very thin layer of batter on it. Remove from oven and place on cooling rack to cool completely.