Lightly grease the bottom and sides of a 9-inch deep-dish pie plate or 9-inch springform pan with butter or neutral oil. If using a springform pan, line the bottom with a round of parchment paper to make releasing the pie easier.

In a medium bowl, stir together the chocolate cookie crumbs, granulated sugar, and fine sea salt. Pour in the melted butter and mix until the crumbs look like wet sand and hold together when pressed. If the mixture seems too dry, add another tablespoon of melted butter.

Pour the crust mixture into the prepared pan and press it firmly across the bottom and up the sides using the bottom of a measuring cup or glass. Pack it tightly so it doesn’t crumble. Chill in the freezer for 15–20 minutes while you soften the ice cream.

Set the chocolate ice cream and coffee ice cream on the counter for 10–15 minutes, just until they’re soft enough to scoop and spread but not melting. The consistency should be like thick soft serve.

Spoon the softened chocolate ice cream into the chilled crust. Spread it into an even layer with an offset spatula or the back of a spoon, pressing gently into the crust so there are no large air pockets. Freeze for 20–30 minutes, until firm on top.

Gently heat the chocolate fudge sauce or hot fudge topping in the microwave in 10–15 second bursts until it is pourable but still thick. If it is too stiff, whisk in the heavy cream a little at a time until smooth. Let it cool for about 5 minutes so it does not melt the ice cream.

Pour the warmed fudge over the chilled chocolate ice cream layer. Spread it carefully all the way to the edges. A few waves and swirls are fine. Freeze again for 15–20 minutes, until the fudge is set and no longer runny.

Spoon the softened coffee ice cream over the firm fudge layer. Spread it out evenly, smoothing the top. If the crust is high, gently press the ice cream down to fit. Cover the pan tightly with plastic wrap or foil.

Freeze the mud pie for at least 4 hours, preferably overnight, until completely firm. This helps you get neat slices that show all the layers without slumping.

About 30 minutes before serving, whip the cold heavy cream with a hand mixer or stand mixer on medium speed until it starts to thicken. Add the powdered sugar, cocoa powder, vanilla, and salt. Continue whipping until medium peaks form—fluffy but still soft enough to spread or pipe.

Spread or pipe the chocolate whipped cream over the frozen mud pie in swirls or rosettes. Garnish with crushed chocolate cookies, chocolate curls, mini chocolate chips, and an extra drizzle of fudge sauce if desired.

Let the finished mud pie sit at room temperature for 10–15 minutes before slicing. Use a sharp knife dipped in hot water and wiped dry between cuts to get clean slices through the crust and frozen layers.