For the crust:
1/4 cu heavy cream
1/2 cup unsweetened cocoa powder, sifted
10 tbsp chilled unsalged butter, cut into 1/4 -inch cubes
10 tbsp powdered sugar
1 1/4 cups all-purpose flour
1 egg yolk
1/2 cup chopped walnuts, toasted
For the filling:
1 1/2 cups whole milk
6 tbsp cornstarch
1/2 tsp table salt
10 tbsp unsalted butter
1 1/2 cups packed dark brown sugar
1/4 cup golden syrup (if you can't find this, use corn syrup)
1/4 cup boiling water
4 egg yolks
1 tbsp whiskey (I used brandy)
1 tsp vanilla extract
For the topping:
1 cup heavy cream
1/4 cup powdered sugar, sifted
2 tsp whiskey (brandy)
1 skor bar (I couldn't find this so I used Heath crunchies)
Heat 1/4 cup heavy cream for the crust in a small saucepan over medium until it bubbles around edges of pan. Place cocoa powder in a bowl, stir in cream; set aside. Beat cubed butter and 10 tbsp powdered sugar in bowl of a stand mixer with a paddle attachment until smooth. Beat in cocoa mixture, half the flour, and 1 egg yolk until smooth. Beat in remaining flour just until combined. Shape dough into a disk, wrap in plastic wrap, and refrigerate at least 1 hour or overnight. Roll chilled dough on a lightly floured surface to 1/4 inch thick; transfer to a 9 - inch pie plate. trim overhang to 1 inch and roll edge under itself. Cover crust with plastic wrap and freeze 15 minutes. Preheat oven to 375 degrees. Place a piece of parchment paper or aluminum foil inside pie shell and fill with pie weights. Bake pie shell 25 - 30 minutes. Remove parchment and weights and bake the crust until crisp and dry, 5 - 10 minutes more; set aside. Sprinkle walnuts on bottom of crust.
Whisk together milk, cornstarch, and salt for slurry in a bowl; set aside. Brown 10 tbsp butter for the filling in a saute pan over medium heat, about 15 minutes. Add brown sugar and golden syrup; bring to a boil. Boil 3 minutes; whisk in boiling water until smooth, boil 1 minute more. Whisk slurry into sugar mixture and increase heat to medium-high. Cook, whisking constantly, until mixture comes to a boil, about 5 minutes; cook 1 minute more and remove from heat.
Drizzle 1 cup butterscotch into 4 egg yolks to temper, whisking constantly. Reduce heat to medium low and gradually whisk tempered mixture back into filling. Simmer filling 1 minute to thicken, whisking constantly; remove from heat. Stir in 1 tbsp whiskey and vanilla; pour filling into crust. Press plastic wrap onto filling to prevent a skin from forming. Cool to room temperature about 1 hour then chill overnight.
Beat heavy cream for the topping in a bowl with a hand mixer on medium to soft peaks. Add 1/4 cup powdered sugar and 2 tsp whiskey, beating until combined. Top pie with whipped cream and garnish with the Heath crunchies.