Line the pan: Use a 9x13-inch baking dish.
Line the bottom with a single, tight layer of graham crackers. Break pieces to fit the edges.
Make the creamy base: In a bowl, beat 8 ounces cream cheese with 1/2 cup powdered sugar and 1 teaspoon vanilla until smooth. Fold in half the whipped topping.
Spread layer one: Smooth the cream cheese mixture over the graham layer.
Add another layer of graham crackers on top.
Mix the pudding: Whisk instant vanilla pudding with cold milk per the package. Let it thicken for 2–3 minutes, then spread over the crackers. Add another layer of graham crackers.
Top with whipped layer: Spread the remaining whipped topping over the final graham layer.
Keep the surface even for clean slices.
Make simple ganache: Heat 3/4 cup heavy cream until steaming (not boiling). Pour over 1 1/2 cups chocolate chips, rest 2 minutes, then stir until glossy. Cool 10 minutes.
Finish: Drizzle or spread the ganache over the top.
Add a pinch of salt or sprinkle with nuts or toffee, if using.
Chill: Cover and refrigerate for at least 4 hours (overnight is best) so the layers set and the crackers soften slightly.
Slice and serve: Use a sharp knife and wipe between cuts for tidy squares. Optional: add fresh berries just before serving.
Prep the pan: Heat oven to 350°F (175°C). Line an 8x8-inch pan with parchment.
Make the base: Crush 2 sleeves of graham crackers into fine crumbs.
Mix with 4 tablespoons melted butter and 1/2 cup brown sugar until it clumps. Press firmly into the pan.
Bake: Bake 8–10 minutes until fragrant and edges look set.
Add layers: While warm, scatter 1 cup chocolate chips and 2 cups mini marshmallows over the crust. Return to oven 3–4 minutes to soften.
Swirl and set: Use a spatula to swirl the melty chocolate and marshmallow.
Optional: warm 1/2 cup peanut butter and drizzle, then swirl again.
Cool completely: Let the pan cool, then chill 30–45 minutes for cleaner cuts. Slice into bars.