Heat heavy cream in a saucepan until just simmering.
Remove from heat and stir in chocolate chips until melted and smooth.
In a bowl, beat cream cheese until creamy.
Add powdered sugar, vanilla extract, and milk; mix until smooth.
Combine the melted chocolate mixture with the cream cheese mixture.
Pour filling into the graham cracker crust and smooth the top.
Sprinkle cocoa powder on top.
Cover and refrigerate for at least 4 hours to set.
Garnish with chocolate shavings before serving.