Vegan Black Sugar Walnut Swiss Roll Cake (Japanese-style)
Black sugar syrup (Kuromitsu) cream filling rolled in fluffy cake, this cake roll is delicious with a Japanese taste with crunchy toasted walnuts inside!
Soak the pitted dates with 120 g water and cashews with enough water to cover respectively for a least 3 hours.
For the cake
Preheat the oven to 175 C / 350 F. Line a baking sheet or jelly roll pan with parchment paper. (jelly roll pan is 10*15 inch, my baking sheet is 27*38 cm)
In a bowl, add the whole wheat pastry flour, corn starch, toasted soy flour (Kinako), baking powder, baking soda, and salt. Give them a mix.
In a blender, add the pitted dates with the soaking water, 320 g water, peanut butter, grapeseed oil. Blend until smooth.
Pour the date mixture into the dry ones and add the apple cider vinegar. Mix until no lumps can be seen.
Pour the batter on the lined baking sheet/jelly roll pan. Drop the pan against the counter a few times to remove the air bubbles.
Bake in the preheated oven at 175 C/350 F for 18-22 minutes. You should know it's done when you insert a toothpick in the middle and it comes out clean.
Remove the pan from the oven and let it cool on a wire rack. In the meantime, let's make the cream filling.
For the filling
Drain out the water from the cashews and give them a gentle rinse.
In a blender, add the soaked cashews, soy milk, coconut cream, and black sugar syrup. Blend until smooth****. It might be runny at first, but it will thicken if you let it sit for a while. (See the texture in the picture above)
Final assembly
Pour 2/3 of the filling mixture onto the cooled cake and spread it out evenly, leaving about 2 cm (an inch) space from the edges.
Place the pan into the freezer for 20-30 minutes to let the cream set up a little bit so it's easier to roll. Put the left filling in the fridge to use later.
Remove the pan from the freezer. Sprinkle the toasted walnuts on top of the cream filling.
Roll the cake up from the shorter side. Press a little bit every time you make a rolling motion.
Enjoy right away or put the cake roll back in the freezer for another 10-20 minutes. It will be firmer and the cutting slices will be prettier.
Take the cake out from the freezer and remove the parchment paper. Pour the left filling onto the cake roll. You can add a little bit of water to the filling if it's too thick to pour. Sprinkle with more toasted walnuts on top. Slice and EAT!
Notes
*Flour: I haven't tested this recipe with other flour so I'm not sure other substitutes will work the same. But all-purpose flour will be a good choice.
**Oil: You can use other neutral-flavor vegetable oil for substitution, like avocado oil and sunflower oil.
***Okinawa black sugar syrup: I cannot find the one I use on Amazon so I'm not sure if you could find it in your country. But this Okinawa black molasses is the most similar one I found on Amazon. I will post a homemade version in the near future.
****Blending: On the first try, I couldn't make the filling super smooth in my Vitamix 64oz blender container, so I changed to use my small 32oz container instead. It turned out to work much better at blending this mixture. I think it's due to the volume of the mixture that it's not enough to bring the large container to work smoothly. So if your blender has trouble blending, double the filling and it should work better. The other way is to use a smaller container (like 32oz container for Vitamix classic blender or 48oz for ascent series)or a smaller blender like a magic bullet.
Storage: Store in the fridge for 3-5 days or 2 weeks in the freezer.