Candied chestnuts (wold in a bottle in the supermarkets)
Make the spongecake. In a bowl, add the egg whites. While mixing with a hand mixer, add the sugar a little bit at a time until completely foamy.
Switch to a rubber spatula. Add the egg yolk and roughly mix in.
Divide the sifted flour into 4-5 batches and fold in. Avoid kneading. Just before the previous batch of flour is blended in, add the next batch.
Mix together the milk and butter. Heat up in the microwave. Add a little bit of the batter from Step 3 and mix.
Add the mixture from Step 4 into the bowl and mix well. The finished batter should drip like a ribbon.
Line the pound cake pan with parchment paper and pour in the batter. Hit the bottom of the pan 2~3 times to get rid of the air. Bake for 20-25 minutes in a 170℃ oven.
When it has finished baking, immediately drop the pan from a high place to get rid of the air. Remove from the pan upside down and cool without removing the paper.
Remove the darkened surfaces with a knife.
Slice into 3 even pieces. Since it's a pound cake shape, I think it will be easy to slice. It will be pretty thin.
Add the Creme Chantilly ingredients to a bowl and whisk. When foamy, add the 30 g of sweet potato for the Creme Chantilly.
Add the ingredients for the syrup in a container and microwave. Dissolve the sugar and set aside to cool.
On the bottom layer of sponge cake, use a brush to coat with the syrup. Then coat with heavy cream and place the middle sponge cake on top. Coat this layer with syrup.
Spread on some heavy cream and arrange 2 thinly sliced candied chestnuts. Put enough cream on to cover the chestnuts and top with the last sponge cake.
Coat with syrup, spread the heavy cream, and let cool in the refrigerator.
Make the sweet potato cream. Boil the potatoes in a pot until soft. While hot, add the sugar, milk, and rum. Mash together.
Strain with a net, or similar item. The potato paste is finished.
After the potato paste has completely cooled, add the creme chantilly and with a rubber spatula, mix well. The Mont Blanc cream is finished.
Attach a Mont Blanc decorating tip to a pastry bag and pipe a good amount onto the top of the cake. Cool in the refrigerator.
When it has cooled, cut from both ends. Decorate with powdered sugar and candied chestnut chopped into small pieces. It's finished.
This is the strawberry version. (Recipe ID: 1666993) "Strawberry Mont Blanc Shortcake".
This is a raspberry cheese version. (Recipe ID: 1733190) "Raspberry Cheese Mont Blanc Shortcake".
Here is a matcha adzuki bean version (Recipe ID: 1765477) "Matcha Chocolate Adzuki Bean Mont Blanc Shortcake".
This is a chocolate version (Recipe ID: 1770284) "Orange Chocolate Mont Blanc Shortcake".
Story Behind this Recipe
I've always thought that a sweet potato Mont Blanc would taste better with a fluffy base rather than a crispier base! So after some experimenting, I was able to make this delicious recipe.
Once you are able to make a delicious sponge cake, the rest is easy. The sponge cake batter is soft and sticks easily, so please don't forget to line the pan with paper. Cut the baking paper to match the size of the pan and cut the four sides so that it fits perfectly.