Place a sheet of parchment paper (or a Silpat) on your counter. Invert the cake over it and peel off the parchment from the bottom of the cake.
Using the cake ring, “stamp” two circles out of the cake. DO NOT DISCARD THE SCRAPS!
For layer #1: Clean the cake ring and place it on a baking sheet lined with parchment. Line the inside with one of the acetate strips. Put all of the cake “scraps” in the ring and press into an even layer, using the back of your hand. Using a pastry brush, soak the cake with half of the Ovaltine soak.
Use the back of a spoon to spread one-fifth of the malt fudge sauce evenly over the cake (if you warm up the sauce it will be easier to spread).
Sprinkle half the malted milk crumbs and one-third of the charred marshmallows evenly over the malt fudge sauce. Use the back of your hand to anchor them in place.
Use the back of a spoon to spread one-fifth of the malt fudge sauce evenly over the crumbs and marshmallows.
For layer #2: Gently tuck the second acetate strip in between the cake ring and the top 1/4” of the first strip – you should have an acetate ring that is about 5” tall. Gently place one cake round (use the less pretty of the two) on top of the frosting. Repeat the soak/malt fudge sauce/crumb/marshmallow/malt fudge sauce steps from layer #1.
For layer #3: Place the remaining cake round on top of the sauce. Cover the top of the cake with the reserved fudge sauce. Garnish with remaining charred marshmallows.
Place the cake – still on the sheet pan – in the freezer and freeze for at least 12 hours (or up to 2 weeks).
At least 3 hours before serving, take the cake out of the freezer, and – using your fingers and thumbs – pop the cake out of the ring. Gently peel off the acetate and place in the fridge. If not serving that day, wrap well in plastic and store in the fridge for up to 5 days.