Step 1

Preheat oven to 450 degrees. Sift the flour and salt together into the bowl of a food processor; add shortening and pulse until pieces are the size of small peas.

Step 2

Sprinkle 1 tablespoon of the cold water over part of the mixture. Pulse again. Add more water as needed and repeat until all the mixture is moistened and just holds together when pressed with fingertips.

Step 3

Flatten dough onto a lightly floured surface by pressing with palm of hand three times across in both directions. Roll from center to edge until 1/8-inch thick.

Step 4

Fit pastry into a 9-inch pie plate and trim 1/2 to 1-inch beyond edge. Fold under and flute edge by pressing dough with forefinger against wedge made of finger and thumb of other hand. Prick bottom and sides well with fork. Bake until golden brown, about 10 to 12 minutes.

Step 5

Carefully remove crust from oven and reduce oven temperature to 325 degrees. Sprinkle chocolate over the bottom of the hot crust. Let chocolate sit for 5 minutes to soften. Using off-set spatula, spread chocolate into even layer; set aside crust.

Step 6

Melt butter in small saucepan over medium-low heat.  Cook, stirring constantly, until butter is dark golden brown and has a nutty aroma, 5 to 7 minutes.  Off heat, slowly stir in bourbon; let cool for 5 minutes.

Step 7

Whisk granulated sugar, brown sugar, cornstarch, and salt together in large bowl until combined. Add eggs, yolk and vanilla, whisking until smooth.

Step 8

Slowly whisk in warm butter mixture until incorporated. Stir in walnuts, then pour filling into chocolate-lined crust.

Step 9

Bake until filling is puffed and center jiggles slightly when pie is gently shaken, 35 to 40 minutes, rotating plate halfway through baking. Let pie cool on wire rack for 4 hours. Slice and serve. (Once sliced, pie can be covered with plastic and refrigerated for up to 2 days.)