01 -
Line an 20 cm or 23 cm square baking pan with parchment paper, leaving overhang on the sides for easy removal. Set aside.
02 -
Place finely chopped chocolate into a bowl. Heat heavy cream in a small saucepan until just simmering. Pour hot cream over chocolate and let sit 2–3 minutes. Stir gently until smooth and combined. Cover and refrigerate while you prepare the meringue.
03 -
Combine egg whites, granulated sugar, and cream of tartar in a heatproof bowl. Place the bowl over a saucepan with 5 cm simmering water, ensuring it does not touch the water. Whisk constantly until sugar dissolves and mixture thins, about 4 minutes. Remove from heat, add vanilla extract, and whip on high speed with a stand or handheld mixer until stiff, glossy peaks form, 5–6 minutes. Reserve 1 heaped cup of meringue, cover tightly, and refrigerate for topping—up to 2 days.
04 -
Spread a very thin layer of marshmallow meringue in the base of the prepared pan to anchor the first layer. Top with a single layer of graham crackers, breaking them for an even fit.
05 -
Spread a layer of marshmallow meringue over the crackers. Add another layer of graham crackers, then a layer of chocolate ganache. Continue layering in the following sequence: graham crackers, meringue, graham crackers, ganache, graham crackers, meringue, graham crackers, and finish with a top layer of chocolate ganache. There will be 6 layers of graham crackers, 4 layers of meringue, and 3 layers of ganache.
06 -
Cover the assembled layers tightly and refrigerate for at least 12 hours or overnight to allow the cake to set.
07 -
When ready to serve, remove reserved meringue from the fridge. If it has deflated, whip briefly. Lift the cake out using parchment overhang and place on a heat-proof serving board. Peel off parchment. Spread meringue on top, swirling with a spoon. Toast the meringue topping with a kitchen torch for a classic campfire finish. Serve immediately, or refrigerate for up to 1 hour before torching.
08 -
Store leftovers tightly covered in the refrigerator or freezer for up to 2 days. Topping may begin to lose structure after refrigeration.