For the Crust
For the Filling
For the Whipped Cream
Make the Crust:
- In a large bowl, whisk together flour, baking powder, and salt. Using a pastry cutter, gradually work shortening into flour until it resembles a coarse meal, 2 to 3 minutes.
- Add white vinegar and 4 tablespoons ice water, then toss mixture together gently. Add remaining ice water 1 tablespoon at a time until dough begins to come together and all flour is moist. (You may need to add more water than called for.)
- Wrap dough in plastic wrap and press down to slightly flatten ball of dough to make rolling easier later. Refrigerate if using within 24 hours; otherwise, freeze.
- When ready to use dough, remove from refrigerator or freezer and thaw, 15 to 30 minutes.
Make the Filling:
- In a small, microwave-safe bowl, melt baking chocolate until stirrable (about 45 seconds). Add hot cocoa powder and stir into chocolate. Set aside to cool completely (it should be cooled to room temperature but still stirrable when added to pie).
- In a large chilled bowl, beat sugar and butter with electric mixer (or stand mixer fitted with paddle attachment) until very light and fluffy, 4 to 5 minutes.
- When melted chocolate is fully cooled, turn mixer on low and drizzle chocolate into butter and sugar mixture. Add vanilla and salt and beat mixture until combined. If using stand mixer, switch to whisk attachment.
- Turn mixer to medium speed and add eggs one at a time, beating 5 minutes between each addition. After 20 minutes of beating, filling should be completely silky and smooth with no grittiness. (If mixture seems to be melting instead of whipping, let chill in fridge 30 minutes and whip again until fluffy.)
- Once pie filling is smooth and silky, pour into baked pie shell. Smooth pie filling and refrigerate until firm, 2 hours, or up to overnight.
Make the Whipped Cream:
- When ready to serve, whip heavy cream and powdered sugar in the bowl of an electric mixer fitted with whisk attachment until stiff peaks form. Pipe whipped cream in dollops around edges of pie. Garnish with chocolate and mini marshmallows.