In a deep dish pie plate, combine graham cracker crumbs, 2 tablespoons sugar, and melted butter until crumbly. Press onto the sides and bottom. Refrigerate.
Chocolate Layer
Melt chocolate chips in microwave on high, 15 seconds at a time, stirring well until melted. Pour chocolate into crust. Refrigerate.
Peanut Butter Mousse
In a large mixing bowl, beat together peanut butter and cream cheese until smooth. Add 1 cup of powdered sugar 1/2 cup at a time, stirring between each addition. In another mixing bowl, whip cream, adding 1/2 cup of powdered sugar while mixing slowly. Whip until stiff peaks form.
Gently fold whipped cream into peanut butter mixture. Pour into crust on top of chocolate layer. Refrigerate at least 1 hour. If desired, top with extra melted chocolate and whipped cream.