1. Preheat your oven to 350°F (175°C).

2. Make the crust: In a bowl, cut the cold butter into the flour using a pastry blender or fork until the mixture resembles coarse crumbs.

3. Gradually add cold water, 1 tablespoon at a time, mixing until a dough forms.

4. Roll out the dough on a lightly floured surface and transfer it to a 9-inch pie plate. Trim and crimp the edges as desired.

5. In a large bowl, whisk together sugar and cocoa powder until well blended.

6. Beat in the eggs one at a time.

7. Stir in the melted butter and vanilla extract.

8. Fold in the chocolate chips (reserve a few to sprinkle on top if desired).

9. Pour the filling into the unbaked crust.

10. Bake for 50–60 minutes, until the edges are set and the center is just slightly jiggly. The pie will finish setting as it cools.

11. Cool at room temperature for at least 2 hours before slicing.