Melt the chocolate chips in a microwave safe bowl. Heat them on high power in 20-30 second intervals, stirring after each, until the chocolate is completely melted.
Stir the melted butter and cocoa powder into the melted chocolate. Set it aside.
Combine the remaining ingredients in a large mixing bowl and use an electric mixer to beat until smooth.
Add the chocolate mixture into the bowl and mix until well combined.
Pour the filling into the pie shells. Place pies onto a baking sheet and bake for 45-50 minutes or until center is set. Allow pies to cool completely before cutting. Serve with whipped cream and dust with cocoa powder (optional).