Mississippi Mud Pie

Preparation - Preheat the oven to 350°F. Line the bottom of a 9-inch springform pan with parchment and lightly grease the lined pan with nonstick cooking spray.

Crust - Make the crust: To the bowl of a food processor fitted with the blade attachment, add the Oreos and salt. Process until the Oreos are finely ground. Add the melted butter and process until the crumbs are evenly moistened.

Crust - Scrape the crumb mixture into the springform pan. Use the flat bottom of a measuring cup or glass to press the mixture evenly in the bottom and about 2 inches up the side of the pan. Chill in the fridge for at least 5 minutes while you make the brownie batter.

Brownie - Make the brownie batter: Add the butter and bittersweet chocolate to a large microwave-safe bowl. Microwave in 30-second intervals, stirring between, until completely melted, about 1 minute total. Add the oil to the butter and chocolate mixture and whisk to combine.

Brownie - Add the granulated sugar and light brown sugar and whisk until combined and no lumps of brown sugar remain. Add the eggs and vanilla and vigorously whisk until the eggs are completely incorporated into the batter.

Brownie - Whisk in the cocoa powder, salt, and baking soda until just combined. Add the pecans (if using) and flour and fold with a rubber spatula until the flour is just incorporated and the pecans are evenly distributed.

Brownie - Bake the brownie layer: Scrape the brownie batter into the Oreo crust and gently smooth if needed, taking care not to disturb the crust. Bake until risen, a crust has formed over the top, and the brownie is just set (it may jiggle very slightly in the center), 30 to 40 minutes. A toothpick inserted about 1 inch from the edge will come out with very moist crumbs. Do not overbake as this can yield a hard brownie once chilled. The brownie will continue to cook through as it cools.

Brownie - Allow the pie base to cool completely in the pan set over a wire rack, at least 1 hour and 15 minutes. The brownie will deflate during cooling, leaving a bit of a lip. If desired, you can use the back of a spoon or offset spatula to lightly press down and level it.

Pudding - Make the pudding: To a large bowl, add the cold milk. Sprinkle the pudding mix over the milk and whisk until thickened to a soft pudding consistency. It should be spoonable and not runny. Scrape the pudding over the cooled brownie layer. Smooth the pudding over the brownie layer, staying within the crust. It's okay if the pudding mounds a little in the center.

Pudding - Press a piece of plastic wrap against the pudding. Transfer the pie to the refrigerator until the pudding layer is set and well chilled, at least 3 hours, but ideally overnight.

Assembly - Finish the pie: When ready to serve, remove the outer ring of the springform pan from the base. If desired, use an offset spatula to slide the pie onto a serving platter.

Assembly - Spoon the whipped cream over the pudding layer, making decorative swoops as desired. Lightly dust the whipped cream with cocoa powder (if using). For the cleanest slices, wipe the knife clean between cuts.

Storage - Leftover pie can be stored in the springform pan covered with plastic wrap or cut into slices and stored in an airtight container in the refrigerator for up to 4 days.