After soaking the sweet potato in water for 10 minutes, microwave at 600 watts for 2 minutes or slightly more to soften it.
When it is still hot, add the unsalted butter and sugar. Quickly mash the potato. The sweetness varies depending on the type of potato so adjust the amount of sugar accordingly.
Purée the mashed potato with a flat or ‘uragoshi’ strainer to remove the stringy fibers.
Press the mixture with a wooden paddle and continue scraping it. This process should be done when the potato is still hot otherwise it’ll be difficult to sieve the mixture.
Flip the strainer over and gather the potato mixture into a bowl. Add the rum and vanilla extract. Lightly combine the mixture.
Add the heavy cream. Mix thoroughly. If the mixture is too thick, add milk a little at a time to adjust its consistency.
Now, the delicious sweet potato cream is ready.
Let’s make the Sweet Potato Mont Blanc. Place the sweet potato cream in a thick pastry bag with a mont blanc nozzle. You can also substitute a small plain nozzle instead.
First, cut out a piece of swiss roll about the size of your ramekin. Place the cake into the ramekin. You can also use your favorite type of sponge cake instead.
Cut the rest of the swiss roll to make another piece of mont blanc.
Now, add the rum to the syrup. Lightly soak the cake with the syrup to taste.
Next, float a bowl of the heavy cream on ice water and add the sugar. Whip the cream until it reaches a stiff peak stage but avoid over-beating it. Fill the ramekin with the whipped cream and even out the surface.
Halve the Kuri Kanroni, a chestnut simmered in syrup and place it onto the whipped cream.
Squeeze the sweet potato cream over the chestnut.
Carefully cover the sweet potato cream with the whipped cream.
Arrange a generous amount of sweet potato cream onto the whipped cream, shaping it into a mountain.
Top with a dollop of whipped cream that can represent a cloud. Garnish with the other half of the chestnut.
Place the mont blanc onto a plate. Finally, sprinkle on the icing sugar.
Removing the stringy fibers from the sweet potato will give the cream an exquisite, smooth texture so don’t forget/skip this step.
If the sweet potato cream is too soft, chill it in the fridge to get a desired consistency. Conversely, if it is too firm, dilute it with milk or heavy cream.