Pudding Filling

Bring the milk and cream to a simmer in a non-reactive medium saucepan over medium heat. IIn a medium bwl, whisk the sugar, eggs and yolks. Add the cornstarch, cocoa and salt and whisk well. Gradually whisk in the warm milk. Return the mixture to the saucepan.

Cook over medium heat, whisking constantly, until the filling comes to a full boil. Remove from the heat and add the chocolate, butter and vanilla. Let stand for a few minutes, then whisk until the chocolate and butter are melted. Strain through a wire sieve into a medium bowl to remove any bits of egg white.

Pour the warm filling into the pie shell. Cover with plastic wrap and pierce wrap so steam can escape. Refrigerate until well chilled, at least 2 hours. The pie can be made up to 1 day ahead, covered and refrigerated.

Topping

In a deep, medium bowl, combine the cream, sugar and vanilla. Using a whisk or a hand-held mixer, whip together until soft peaks form.

Spoon the whipped cream into the center of the chilled pie, mounding it casually so cream will spread naturally. Scatter the toffee pieces over the top just before serving. Serve chilled, cut into wedges with a sharp knife.