Place the flour, cocoa, sugar, and salt in a large mixing bowl and whisk to combine.

Stir in the oil, until the mixture resembles coarse meal.

Add the butter slices, tossing to coat.

Stir in the water, a tablespoon at a time, just until the dough gathers itself into a ball.

Flatten the dough into a disc shape, wrap tightly, and chill in the refrigerator for 1 hour.

On a lightly floured surface, pat or roll the dough into a rectangle about ½-inch thick.  Fold it into thirds, like a letter.  Roll out again to a thickness of ½-inch.  Turn the dough 90 degrees and repeat two more times.

Wrap the dough in plastic wrap and refrigerate for 2 hours minimum.

Dust the work surface with flour, and roll the dough out to an inch or two larger than your pie dish.

Roll the dough around the rolling pin, and transfer to the dish.

Trim off any excess, then roll and crimp the edge.

Bake for 20 minutes at 350 degrees F.

Cool completely before filling.

Place the chocolate, water, cocoa powder, sugar, and salt in a large bowl and microwave in 30 second increments, stirring, for 1 to 2 minutes, or until melted and smooth.

Fold in the whipped cream and vanilla until combined.

Transfer to the cooled pie crust, cover loosely, and refrigerate for two hours (or preferably overnight).

Garnish with whipped cream and chocolate shavings.