How to Make It
Preheat the oven to 325ºF.
Grease and lightly flour a 9 x 5 loaf pan.
Sift together flours, soda, and cinnamon in a medium mixing bowl and set aside.
In a large mixing bowl, combine hot water, brown sugar, oil, malt, and salt. Mix well by hand, but don’t overbeat.
Using a spatula, add flour mixture to water sugar mixture gradually until fully incorporated, or until the batter becomes smooth.
Carefully beat in eggs with spatula until incorporated. (At this point, the batter should be very thin.)
Pour the batter into the greased and lightly floured pan and bake for 1 hour and 15 minutes. Test readiness by inserting a skewer. When the skewer comes out clean, the loaf is done. Remove from the oven and let cool on a rack until the loaf reaches room temperature.
Once cooled, wrap with plastic wrap and place in freezer for 30 minutes to an hour, or until the loaf is firm. This will make it much easier to slice.
Grate chocolate bars and set aside.
Take the partially frozen loaf and slice at ¼- to ½-inch thickness (your preference)—either length-wise for a full “tartine” or in 5-inch squares for a portion closer to the size of traditional graham crackers.
Lightly toast graham tartine slices before adding toppings.
Sprinkle grated chocolate over top and finish with six marshmallows. Set under a broiler until marshmallows are golden.
Slice into three bite-size servings and feast.