In a medium bowl, whisk together flour, salt, and granulated sugar. Cut in chilled shortening until it resembles coarse crumbs. Gradually add ice water, one tablespoon at a time, mixing until the dough just comes together. Do not overmix. Form into a flat disk, wrap in plastic wrap, and chill for at least 30 minutes.

Preheat oven to 375°F (190°C). On a lightly floured surface, roll out the dough into a 12-inch circle and transfer to a 9-inch pie plate. Trim and crimp the edges. Line the crust with parchment paper, fill with pie weights or dried beans, and bake for 15 minutes. Remove parchment and weights, then bake for another 5-7 minutes until lightly golden. Let cool completely on a wire rack.

In a large bowl, cream together softened butter and granulated sugar until light and fluffy. Beat in powdered sugar until combined. Add melted semisweet chocolate, vanilla extract, and salt, beating until smooth and glossy. Beat in room temperature eggs, one at a time, beating well after each addition.

In a separate chilled bowl, whip heavy whipping cream until stiff peaks form. Gently fold the whipped cream into the chocolate mixture until just combined.

Pour the chocolate filling into the cooled pie crust. Cover and refrigerate for at least 4 hours, or until firm.

Just before serving, whip heavy whipping cream, powdered sugar, and vanilla extract in a chilled bowl until stiff peaks form.

Spoon or pipe the whipped topping over the chilled pie. Garnish with chocolate shavings or cocoa powder if desired. Slice and serve.