Line the bottom of a 9-inch tart pan with parchment paper and lightly spray it with nonstick spray. Set aside.

Combine chocolate chips and vegetable oil in a microwave-safe bowl. Microwave for 45-55 seconds, then stir until smooth.

Pour ½ of the melted chocolate into the prepared tart pan and spread evenly over the bottom and sides. Chill in refrigerator.

Whisk together powdered sugar and graham cracker crumbs in a large bowl. Set aside.

Heat peanut butter and butter in the microwave for 45 seconds, then stir to combine.

Add the peanut butter mixture to the powdered sugar and crumb mixture, and stir until fully incorporated.

Spread the peanut butter filling into the chilled chocolate shell and smooth the top.

Pour the remaining melted chocolate over the peanut butter layer and smooth to edges.

Chill the pie in refrigerator for at least 4 hours or overnight.

Remove the pie from the fridge, flip upside down on a serving platter, then peel off the parchment paper.

Slice into wedges and serve.