Step 1

Preheat the oven to 375 degrees.

Step 2

Combine the chocolate wafers, sugar and butter in bowl of food processor fitted with the blade attachment and pulse until the cookies are finely crushed. Press the mixture firmly into a 9-inch pie pan (spread some of the crumbs up the sides first, making the crust just shy of 1/4-inch thick, then press the remaining crumbs onto the bottom; use a the bottom of a measuring cup or glass to even out, if you like). Bake for 10 minutes until crisp.

Step 3

Combine the sugar, cornstarch and salt in a heavy medium saucepan. Whisk gently until combined.

Step 4

In a bowl or large measuring cup, whisk together the milk and egg yolks. Add the milk mixture to the saucepan in a slow and steady stream, whisking until the mixture is smooth. Cook over medium-high heat, whisking frequently, until the mixture starts to bubble and thicken, 6-8 minutes. Immediately turn the heat down to a simmer and cook -- whisking constantly, especially around the edges -- for one more minute until thick. (The constant stirring and low heat prevents the eggs from scrambling. Be sure to scrape the whisk against the bottom and edges of the pan where the mixture is more likely to overheat.) Off the heat, immediately add the chopped chocolate, butter and vanilla extract; whisk until evenly combined.

Step 5

Pour the filling into the crust and smooth the top. Press a piece of saran wrap directly over surface of the filling to prevent a film from forming; chill in the refrigerator for at least 8 hours or overnight.

Step 6

(Up to 3 hours before serving) Place the heavy cream in chilled mixing bowl. Using an electric mixer, whip on medium-low speed until the whisk or beaters begin to leave tracks in the cream. Add sugar and whip until the cream holds medium, silky peaks. Go slowly towards the end; if it gets grainy or curdled, you’ve gone too far. Spread the whipped cream over the filling, leaving some of the chocolate filling showing around the edges. Sprinkle with the grated chocolate and refrigerate until ready to serve.

Step 7

*Nabisco cookies available in the cookie aisle at most major supermarkets. Sometimes they can be hard to spot. At my local Giant, they’re on the top shelf near the Oreos.