For the crust: Add the chocolate sandwich cookies to a food processor and pulse until finely ground, then add the salt and pulse again to combine. Drizzle the melted butter into the food processor while running until the mixture resembles wet sand. Press the mixture evenly and firmly into the bottom and up the sides of a 9-inch pie plate. Place in the freezer for 30 minutes to 1 hour.
For the pie: Stir together the chocolate with the condensed milk and vegetable oil in a small saucepan over medium-low heat and cook, stirring constantly, until smooth, melted and combined. Pour the chocolate mixture into the bottom of the chilled pie crust, using an offset spatula to spread into an even layer. Sprinkle the pecans over the chocolate layer and set aside.
In a medium bowl, whisk together the pudding mix with the cold milk until very thick. Fold 1/2 cup whipped topping into the pudding, then spread evenly over the chocolate layer. Top with the remaining whipped topping. Refrigerate until set, 4 hours or up to overnight.
For the garnish: Add the heavy cream and chocolate chips to a small bowl. Microwave for 30 seconds, then stir and microwave again for 10 seconds more. Repeat in 10-second increments until the chocolate is smooth. Sprinkle the pie with the crushed cookies and chopped pecans, then drizzle with the chocolate before serving.