• You’re building this rich chocolate dessert in layers, so take it step by step and give each layer time to set. Here’s exactly how to do it.

Prep the pan and oven

• Preheat your oven to 350°F (180°C).
• Lightly grease a 9-inch deep-dish pie plate (or a 9-inch springform pan) and set it aside.
• This early prep makes assembling the crunchy chocolate cookie crust much smoother.

Make the chocolate cookie crust

• In a medium bowl, combine the crushed chocolate sandwich cookies, granulated sugar, and pinch of salt.
• Pour in the melted butter and stir until every crumb is evenly coated and the mixture looks like wet sand.
• Press the crumbs firmly into the bottom and slightly up the sides of your prepared pan, using the bottom of a measuring cup to compact the crust.
• Bake for 8–10 minutes, just until the crust is fragrant and set.
• Remove from the oven and let it cool slightly while you prepare the fudgy brownie layer.
• Pressing the crumbs firmly helps prevent a crumbly base and gives your mississippi mud pie a sturdy, sliceable crust.

Bake the fudgy brownie layer

• Place the butter and semisweet chocolate in a heatproof bowl set over a saucepan of gently simmering water (or use short bursts in the microwave). Heat, stirring often, until melted and smooth.
• Whisk in the granulated sugar and brown sugar while the mixture is still warm.
• Add the room-temperature eggs and vanilla extract, whisking until the mixture looks glossy and well combined.
• Sift the flour, cocoa powder, and salt over the bowl. Gently fold with a spatula just until no dry streaks remain.
• Pour the brownie batter over the warm crust and spread it into an even layer.
• Bake for 15–18 minutes, or until the edges are set and a toothpick inserted near the center comes out with a few moist crumbs (not wet batter).
• Transfer the pan to a wire cooling rack and let the brownie layer cool completely.
• Letting the brownie layer cool completely is key—if it’s too warm, the creamy chocolate filling can turn runny instead of setting into smooth, silky layers.

Cook the creamy chocolate filling

• In a medium saucepan (off the heat), whisk together the sugar, cocoa powder, cornstarch, and salt until no lumps remain.
• Add the egg yolks and whisk into a thick paste.
• Gradually pour in the whole milk and heavy cream, whisking constantly so the mixture stays smooth.
• Place the saucepan over medium heat and cook, whisking continuously, until the mixture starts to bubble and thickens to a pudding-like consistency, about 5–8 minutes.
• Remove from the heat and immediately stir in the chopped chocolate and vanilla extract until fully melted and glossy.
• Let the filling cool for 10–15 minutes, stirring occasionally. For extra-smooth results, press a piece of plastic wrap directly onto the surface to prevent a skin from forming.
• If you see small lumps, you can strain the warm chocolate filling through a fine-mesh sieve before pouring it over the brownie layer.

Assemble the layers and chill

• Once the brownie layer is completely cool, gently pour the slightly cooled chocolate filling over it.
• Use an offset spatula or the back of a spoon to spread the filling into an even, level layer.
• Cover the pie loosely with plastic wrap (avoid pressing directly on the surface if you’ve already removed any skin).
• Chill in the refrigerator for at least 4 hours, or until the chocolate filling is fully set and the mississippi mud pie feels firm when gently tapped.
• This chilling time transforms the pie from a warm mixture of layers into a sliceable, restaurant-worthy rich chocolate dessert.

Whip the topping and finish the pie

• In a chilled mixing bowl, beat the cold heavy cream, powdered sugar, and vanilla on medium-high speed until soft to medium peaks form.
• Dollop the whipped cream over the chilled pie, then spread it gently to the edges in swoops and swirls.
• Garnish with chocolate shavings, curls, or mini chocolate chips for an extra indulgent finish.
• For a fun twist, you can also scatter chopped pecans or mini marshmallows on top to echo classic Mississippi mud pie textures.

Slice and serve

• For the cleanest slices, refrigerate the topped pie for another 20–30 minutes before cutting.
• Run a sharp knife under hot water, wipe it dry, and slice straight down through the layers, wiping the blade between cuts.
• Now you’re ready to serve a beautifully layered, fudgy, creamy Mississippi mud pie that looks impressive and tastes like a true indulgent chocolate dream.