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

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

Pour half of the melted chocolate into the prepared tart pan; spread evenly over the bottom and sides. Chill while preparing the filling.

In a large bowl, whisk together powdered sugar and graham cracker crumbs. Set aside.

In a microwave-safe bowl, heat the peanut butter and butter for 45 seconds. Mix thoroughly to combine.

Pour the peanut butter mixture into the dry ingredients and stir until well combined.

Spread the peanut butter filling over the chocolate layer in the tart pan, smoothing evenly.

Top the peanut butter layer with the remaining melted chocolate, smoothing to the edges.

Gently tap the tart pan to settle the chocolate, then refrigerate for at least 4 hours or overnight.

Before serving, remove from refrigerator, invert onto a plate, and peel off the parchment paper. Slice and serve.