Lightly spray a 9-inch tart pan with nonstick cooking spray. Line the bottom with a circle of parchment paper and spray the parchment lightly as well. Set the prepared pan aside.

In a large microwave-safe bowl, combine the milk chocolate chips and vegetable oil. Heat the mixture in the microwave in 30–45 second increments on HIGH power, stirring thoroughly after each interval. Continue this process until the chocolate is fully melted and smooth.

Pour approximately half of the melted chocolate into the tart pan. Using an offset spatula or the back of a spoon, spread the chocolate evenly across the bottom and up the sides of the pan. Transfer the pan to the refrigerator to chill until the chocolate layer has set.

In a separate microwave-safe bowl, combine the crunchy peanut butter and salted butter. Microwave the mixture in short intervals of 30–45 seconds, stirring between each, until both are fully melted and smooth.

In a large mixing bowl, whisk together the confectioners’ sugar and graham cracker crumbs until well blended. Pour the warm peanut butter mixture into the dry ingredients and stir until a cohesive filling is formed.

Remove the tart pan from the refrigerator. Spoon the peanut butter mixture into the chocolate shell, pressing gently to create an even layer. Pour the remaining melted chocolate over the peanut butter layer and spread it evenly, ensuring the top is smooth and the chocolate reaches the edges.

Return the pie to the refrigerator and chill for a minimum of 4 hours, or until fully set. Once chilled, slice and serve. Store any leftovers refrigerated.