Prep your pan. Use a 9-inch springform pan and line the bottom with parchment for easy release.
Lightly grease the sides if you like.
Make the crust. Crush the biscuits into fine crumbs using a food processor or a zip-top bag and rolling pin. Stir in the sugar and salt, then mix in the melted butter until the crumbs look like damp sand.
Press and chill. Pour the crumbs into the pan and press firmly across the base and slightly up the sides. Use the bottom of a measuring cup to get an even, tight layer.
Chill for at least 20 minutes while you make the filling.
Soften the cream cheese. Let the cream cheese sit at room temperature for 20–30 minutes. This prevents lumps and makes a smoother filling.
Whip the cream. In a cold bowl, whip the heavy cream with a pinch of salt to medium-stiff peaks. Set aside in the fridge.
If using instant pudding mix for stability, sprinkle it in as you whip.
Optional gelatin step. If you prefer a firmer set, sprinkle gelatin over cold water in a small bowl and let it bloom for 5 minutes. Microwave for 8–10 seconds until melted and fluid. Cool slightly; it should be warm but not hot.
Beat the base. In a large bowl, beat the softened cream cheese until smooth.
Add powdered sugar, lemon zest, vanilla, and a pinch of salt. Beat until creamy and no lumps remain, scraping the bowl as needed.
Add the lemon juice. With the mixer on low, slowly stream in the lemon juice. Mix just until combined.
If using gelatin, blend in a tablespoon of the cheesecake mixture to temper it, then pour the gelatin into the bowl while mixing on low to evenly distribute.
Fold in the cream. Gently fold the whipped cream into the lemon mixture in two additions. Stop as soon as it looks smooth and airy—overmixing can deflate it.
Fill and smooth. Spoon the filling over the chilled crust. Smooth the top with an offset spatula.
Tap the pan lightly on the counter to pop any air bubbles.
Chill to set. Cover and refrigerate for at least 6 hours, preferably overnight. Longer chill = cleaner slices.
Garnish and serve. Loosen the edges with a thin knife and release the springform. Top with whipped cream, berries, lemon twists, or a drizzle of lemon curd. Slice with a warm knife for sharp edges, wiping between cuts.