Step 1

Preheat the oven to 400˚F. On a lightly floured surface, roll the pie dough into a 12-inch circle. Transfer the crust to a 9-inch pie plate (not deep dish). Tuck the edges of the crust under to be even with the edge of the pie plate and crimp as desired. Place the crust in the refrigerator for 60 minutes (or freezer for 30 minutes).

Step 2

Line the inside of the crust with parchment paper, then fill with baking weights or dried beans. Bake until the edges of the crust are very lightly golden, 18 to 22 minutes. Remove the pie weights and parchment paper. Return the crust to the oven and bake until the crust is lightly golden all over, 10 to 12 minutes more. Let cool to room temperature. Reduce the oven to 350˚F

Step 3

Place ⅔ cup chocolate chips in a medium microwave-safe bowl. Microwave the mixture at 50% power in 15-second intervals until the chocolate is melted, about 1 minute. Stir in the vegetable oil and cocoa powder, mixing until well combined.

Step 4

In a large bowl, whisk the brown sugar, eggs, and vanilla until lighter in color. Pour the chocolate mixture into the brown sugar mixture, whisking until combined. Stir in the flour and salt until just combined. Fold in the walnuts, if using, and the remaining ⅔ cup chocolate chips until just combined.

Step 5

Pour the batter into the prepared pie shell, spreading into an even layer.

Step 6

Bake until the surface is matte and a toothpick inserted in the center comes out with moist crumbs, 40 to 45 minutes.

Step 7

Allow the pie to cool at least 1 hour before slicing. Serve with ice cream, if you like.