To make the crust, crush the saltine crackers. You can get a really fine, uniform texture by using a food processor. In medium mixing bowl, add the crushed crackers with the sugar, melted butter, and vanilla extract. Stir well to combine. Lightly butter a springform cheesecake pan and add the crust mixture to the pan. Use the bottom of a mixing cup or spoon to press the mixture into the pan, so it’s uniform throughout (or close).
In a blender, combine the softened cream cheese, melted chocolate, sugar, milk, and peanut butter. Blend until combined well and smooth. Pour the mixture onto the baked crust, sprinkle with sea salt, and cover with aluminum foil. Freeze for at least an hour, but you can make this days ahead if you like. Just allow to soften some before serving so you’ll be able to slice it easily.
In a stand mixer, add the heavy whipping cream and with the whisk attachment beat the milk on high for a few minutes. Slowly add the sugar and vanilla extract while the mixer is running. Once the mixture can form soft peaks, or looks like whipped cream, you’re done. You can also do this by hand if you don’t own a stand mixer. Before serving top the pie with the whipped cream and, if you want, some chocolate shavings.
If you have a peanut allergy or just don't like peanut butter, you can swap that out for any other nut butter you prefer.