First, let’s make the potato filling. Soak the peeled Japanese sweet potato in a generous amount of water for about 10 minutes to reduce any unwanted flavors.
Strain the potato and place it into a pot of water. Heat it on low heat. Gradually heating the potato will help to increase its sweetness.
Cook until it softens and slightly crumbles.
Strain the potato thoroughly.
Place it into a bowl. When it is still hot, add the salt and sugar.
Mash the potato with a masher. The sweetness varies depending on the type of potato so adjust the amount of sugar accordingly.
Thoroughly mix to combine.
Place the potato filling into a mold covered with plastic wrap. If the filling is too soft, microwave it to reduce the water before placing it in the container.
Shape the potato into a rectangle about 4x4x14cm (1.6"x1.6"x5.5"). Cover with the plastic wrap.
Adjust the shape with a scraper to make it more presentable.
Chill the potato filling in the fridge or freezer until the inside is firm.
Let’s make the batter for the wrapper. Add a small amount of water to the shiratamako or mochiko, sweet rice flour. Mix thoroughly. When the clumps of flour have disappeared, add the rest of the water. Mix again.
Then, add the cake flour and a pinch of salt.
Combine the mixture evenly. The batter should be relatively thin as shown.
Next, cut the chilled potato filling into 2cm (0.8") thick slices. Dampen the knife for each cut to help make a clean cut. You’ll have 7 pieces in total.
Let’s make the kintsuba. Heat a pan on medium heat and coat it with vegetable oil using a paper towel.
Dip one side of the square surface into the batter.
Sprinkle the toasted black sesame seeds on the center.
Place it onto the pan and lightly press it. Repeat the process for the rest of the pieces.
When the batter is dry, remove and dip the other side into the batter.
Place it onto the pan. Repeat the process for the rest of the kintsuba and lightly press them again.
Now, the top and bottom are ready. Repeat the process for the rest of the 4 sides.
They are hot so be sure to use a kitchen glove or spatula to avoid burning yourself.
Place each kintsuba onto a cooling rack as soon as it is ready.
When the wrapper of the leftover kintsuba has become firm, try deep-frying them. They are also delicious and you’ll enjoy a different, crisp texture.
Depending on the type of sweet potato, the water content may vary. If the filling is too dry, add boiled milk to adjust the consistency.