Pretzel s'mores cake

Directions

1. Add chocolate to a large mixing bowl and set aside.
2. In a second large mixing bowl, vigorously whisk together egg yolks and sugar until combined, velvety, and paler in colour.
3. Add cream to a small saucepan and heat on low to a gentle simmer - we’re looking for tiny, quivering bubbles here, rather than large ones. Note: It’s important to always heat cream (and milk for that matter) slowly to prevent it from boiling over, as well as from scorching the pan. Once gently simmering, turn off the heat and slowly temper the eggs by pouring about a ladleful of the hot cream into the egg yolks while whisking vigorously. Once combined, slowly pour in the rest of the cream in a thin stream while continuing to whisk.
4. Pour cream mixture back into the saucepan and set over low heat to cook the custard. Stay at the stove now and continue stirring with a wooden spoon as it cooks for about six minutes. As you stir, address all corners of the saucepan with the spoon and check if any curdling is happening. If you see any little lumps lower the heat and keep stirring. You’ll know the custard is cooked when it richly coats the back of a spoon and a line drawn through it with your finger stays intact – a classic cooking technique called “cuit a la nappe”. 
5. Place a fine mesh sieve over the bowl of chocolate and pour the hot cream through – this is your insurance against any lumps. Allow the custard to melt the chocolate a couple minutes before using your whisk to stir and combine. Cover with plastic wrap pressed gently onto the surface of the custard and cool to room temperature (this prevents a “skin” from developing). Once cooled, refrigerate about three hours to set to a thick, pudding-like consistency.
6. Meanwhile, line a loaf pan with plastic wrap leaving enough of an overhang to wrap over the bottom of the cake once layered.

Assembly:

1. Once set, spread 1/2 cup of the chocolate in the bottom of the pan, spreading edge to edge with the back of a spoon or an offset spatula. Layer graham crackers in a single layer, trimmed as needed to fit pan (approximately four crackers here). 
2. Top with 1/2 cup pudding, spreading to cover, then half of the crushed pretzels, and then half of the marshmallows. Next, top with 1/2 cup chocolate (dropped in dollops for easy spreading) and smooth to cover, adding a couple more tablespoons of chocolate as needed to cover the marshmallows. 
3. Cover with a single layer of graham crackers, trimming to fit pan, and then roughly 1/2 cup chocolate to cover again. Repeat with pretzel and marshmallow layers, chocolate, and the final layer of graham crackers. Cover with remaining chocolate, spread to all edges, and then cover with the plastic wrap overhang and refrigerate overnight. 
4. Note: You want the chocolate custard to touch every inch of graham cracker because that’s what’ll make them soften to a cake-like consistency.

To serve:

1. Whip the 1/2 cup cream until firm peaks. Remove cover on cake and invert onto a platter. Unwrap, top with whipped cream, and slice to serve. Keep refrigerated.