Chocolate Mousse Pie

​1 (9 ounce) package thin chocolate wafer cookies
¾ cup butter, divided
1/3 cup water
1 ¾ cups semisweet chocolate chips
2 ½ cups mini marshmallows
4 cups heavy cream, divided
¼ cup powdered sugar
2 tablespoons cocoa powder
 
1.  Pulverize cookies in food processor.  Melt ½ cup butter and add to cookie crumbs; pulse to combine.  Transfer to a deep dish pie plate and press evenly on the bottom and up the sides.  Refrigerate for at least 30 minutes.
 
2.  Bring water to a boil in a large saucepan over medium.  Add remaining butter, chocolate chips and marshmallows and reduce heat to low; cook, stirring, until melted and smooth.  Transfer to a large bowl and set aside to cool to room temperature, stirring occasionally.
 
3.  Beat 2 ½ cups of cream until stiff peaks form.  Carefully and gradually fold whipped cream into chocolate mixture.  Transfer to prepared crust and refrigerate for at least 2 hours.
 
4.  Whisk together remaining 1 ½ cups cream, powdered sugar and cocoa powder.  Beat until stiff peaks form, then spread over mousse layer.  Refrigerate for at least 2 hours and up to one day before serving. 
 
Revised November 2017