Prepare the filling mixture by combining cream cheese, powdered sugar, and cocoa powder in a bowl.
Add in the Irish cream liqueur and vanilla extract, mixing until well combined.
In a separate bowl, whip the heavy cream until stiff peaks form.
Fold the whipped cream into the cream mixture gently.
Pour the filling into the prepared pie crust and smooth the top with a spatula.
Chill the pie in the refrigerator for at least 4 hours, or until set.
Before serving, garnish with additional whipped cream or chocolate shavings, if desired.