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1
Preheat the oven to 350 F.
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2
To make the crust, use a food processor to combine the flour, cocoa powder, granulated sugar, powdered sugar, and salt.
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3
Add the butter and pulse until it is cut into the dry mixture and the mixture looks like coarse meal.
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4
Transfer the mixture to a medium bowl and add the walnuts.
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5
In a separate bowl, combine the vanilla and 2 teaspoons water.
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6
Stir the dry mixture while adding the vanilla and water until evenly moistened.
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7
If the dough is dry, add another 1 to 2 teaspoons of water, as needed.
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When it is finished, the dough will look crumbly but should hold together when squeezed lightly with your fingers.
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9
Spread an even layer of the mixture in the bottom of a 9-inch springform pan or cake pan with a removable bottom.
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10
Lay a sheet of plastic wrap over the mixture and, using your hands, press the crust evenly into the bottom of the pan and up the sides of the pan to a height of 1 1/4 to 1 1/2 inches.
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The crust on the bottom of the pan should be about 1/8 inch thick.
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12
(You might not use all of the mixture.)
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13
Bake the crust for 20 to 25 minutes, or until it is dry and fragrant.
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14
Set aside and let cool to room temperature.
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15
Chill the crust until ready to use.
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16
While the crust is baking, begin preparing the filling by melting the chocolate.
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17
First, place the chocolate pieces in a medium metal bowl.
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18
Then fill a medium saucepan with 1 inch hot water and heat over medium-low heat.
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Finally, place the metal bowl on top of the saucepan and melt the chocolate, stirring occasionally.
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20
(Alternatively, you can melt the mixture in a double boiler or in a microwave-safe bowl in the microwave in 15-second spurts.)
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Once the chocolate is melted, remove it from the heat.
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22
Put the butter in the bowl of an electric mixer fitted with the wire whip attachment.
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23
(You could also use a handheld mixer.)
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24
Whip the butter on medium-high until it is light and fluffy, about 2 minutes, scraping the bowl once or twice while mixing.
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25
In a separate bowl, dissolve the espresso powder into the vanilla.
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26
Add the sugar and the coffee mixture to the butter and beat for 2 minutes on medium-high.
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27
Pour in the melted chocolate and continue to mix for 2 minutes, scraping the bowl once or twice while mixing.
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28
With the machine running, slowly pour the cream into the butter mixture.
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29
Continue to whip the mixture until thoroughly combined, scraping the bowl once or twice while mixing.
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30
Spread the mixture into the cooled shell.
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31
(If the shell is still warm, it will melt the chocolate mixture.)
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32
Cover the pie with plastic wrap and refrigerate for at least 3 hours or overnight.
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33
After the pie is chilled, make the topping by whipping the cream in the bowl of an electric mixer fitted with the wire whip attachment, or use a handheld mixer.
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34
Whip until soft peaks form.
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35
Add the vanilla and 1/3 cup powdered sugar and whip until thoroughly combined, about 30 seconds.
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36
Taste for sweetness and whip in more powdered sugar if desired.
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37
Spread the topping on the pie just before serving.
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38
Remove the ring from the pan, keeping the pie on the flat piece.
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39
Use a warm knife to slice the pie.
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40
The pie will keep, covered, for up to 5 days in the refrigerator.
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41
Add the topping just before serving.
