Step 1Scald the milk in a saucepan.
Step 2Stir together the sugar and egg yolks in a bowl until smooth. Mix a little of the hot milk with the eggs, then stir the mixture into the milk.
Step 3Sift the cocoa into a bowl. Add a little of the hot milk mixture and stir, then add the cocoa mixture to the milk mixture. Cook over medium heat, stirring constantly, until the liquid coats the back of a wooden spoon, about 2 to 3 minutes.
Step 4Remove from heat. Stir the gelatin into the hot custard. Place the pan over a bowl of ice. Chill, stirring occasionally, until the custard forms a mound when dropped from a spoon.
Step 5Whip 1 cup cream until it forms stiff peaks. Fold into the custard.
Step 6Fill the pie crust with the custard mixture and refrigerate until set, several hours or overnight.
Step 7In a small bowl, whip the remaining 1 cup cream. Stir in the powdered sugar. Spread evenly over the filling and sprinkle with grated chocolate.