Take the crumbs and melted butter and combine. Press into your 9 inch pie plate, creating a bottom and sides. Put into the fridge to firm up while you make the rest of the pie.
Take 1/2 cup of the chips and mix into your softened ice cream then spread onto your pie crust. Place this into the freezer.
Melt the rest of your baking chips in a saucepan over medium heat with 1/2 cup whipped cream, stirring constantly.
Remove from the heat and then stir in the egg yolks well.
Place back onto the stove and heat for another 3-5 minutes, until the mixture started to thicken, stirring it every now and them. It's really important NOT to let this mixture boil at this point. Remove from the heat and cool to room temperature.
Whip the last cup of whipping cream until stiff peaks form and then fold into the chocolate mixture. This is why you absolutely cannot have that mixture warm but still need it fairly fluid, you have to incorporate it.
Once it's folded in all beautifully, you have completed your mousse!
Spread over the ice cream in the crust and then place it back into the freezer for a solid 4 hours.
When you are going to serve it, let it stand at room temperature for 10 minutes.