Lightly grease a 9×13-inch baking dish, or line it with parchment paper with overhang for easier lifting and slicing. A glass dish is nice if you want to show off the layers.
In a large mixing bowl, beat the softened cream cheese with an electric mixer on medium speed until smooth and fluffy, about 1–2 minutes. Scrape down the sides so there are no lumps.
8 oz cream cheese
Add the powdered sugar, vanilla extract, and salt to the cream cheese. Beat again until fully combined and creamy; it should look like a thick, shiny frosting.
1 cup powdered sugar, 2 teaspoons pure vanilla extract, 1/4 teaspoon fine sea salt
In a second large, chilled bowl, pour in the cold heavy whipping cream. Beat on medium-high speed until stiff peaks form, 3–5 minutes. The cream should stand up when you lift the beaters and not flop over.
3 cups heavy whipping cream
Gently fold the whipped cream into the cream cheese mixture in 2–3 batches using a spatula. Use light, scooping motions so you don’t deflate the cream. Taste and adjust sweetness if needed.
3 cups heavy whipping cream, 8 oz cream cheese, 1 cup powdered sugar, 2 teaspoons pure vanilla extract, 1/4 teaspoon fine sea salt
For a chocolate icebox cake, sift 2 tablespoons unsweetened cocoa powder into part or all of the cream mixture and gently fold until no streaks remain.
2 tablespoons unsweetened cocoa powder
Arrange a single layer of graham cracker sheets (or wafers) across the bottom of the prepared pan. Break pieces as needed to cover the entire surface. A few small gaps are fine.
45-55 sheets graham crackers, 14-16 oz vanilla wafers or thin chocolate wafers
Spoon about one-third of the whipped cream filling over the crackers and spread it into an even layer about 1/2–3/4 inch thick with an offset spatula or the back of a spoon.
If using, sprinkle a handful of sliced berries or mini chocolate chips over the cream, keeping them in a fairly even single layer so the cake slices cleanly.
1-1 1/2 cups fresh berries, 1/2 cup mini chocolate chips or dark chocolate
Add another layer of graham crackers or wafers, then another layer of cream. Repeat until you have 3–4 layers of cookies and finish with a thick layer of cream on top. Gently press each cookie layer down so it makes good contact with the cream.
3 cups heavy whipping cream, 8 oz cream cheese, 1 cup powdered sugar, 2 teaspoons pure vanilla extract, 1/4 teaspoon fine sea salt, 45-55 sheets graham crackers, 14-16 oz vanilla wafers or thin chocolate wafers
Cover the dish tightly with plastic wrap or a lid and refrigerate for at least 4 hours, preferably 8–12 hours or overnight, until the cookie layers have softened into a cake-like texture.
Just before serving, top the cake with extra berries, chocolate shavings, cookie crumbs, or crushed graham crackers. Drizzle with caramel or chocolate sauce if desired. Slice with a sharp knife, wiping the blade between cuts for clean slices.
1-1 1/2 cups fresh berries, 1/2 cup mini chocolate chips or dark chocolate, chocolate shavings, cookie crumbs, or crushed graham crackers, caramel or chocolate sauce