This is basically the same as Recipe ID: 2050212, so please refer to that recipe and make it in the same manner.
Instead of the round cake pan from Recipe ID: 2050212, line a small heat-resistant stainless steel pan, like one from the 100 yen shop, with paper.
I used a 26 x 13 cm shallow stainless steel pan that I bought at the 100 yen store.
Pour step 1 from Recipe ID: 2050212 into the shallow pan from Step 2, and spread it out with a rubber spatula. Drop the dish several times from a height of about 10cm to prevent it from shrinking.
The shallow pan I am using is a bit big for the batter, so I spread the dough out all the way to the edges, and adjust it a bit in the center.
Bake in the oven at 160℃ for 10 minutes. Drop the pan several times from a height of about 10cm to prevent it from shrinking.
Let cool inside the shallow pan with the paper still intact. Cover the sponge cake with plastic wrap or aluminum foil to keep it from drying out.
Peel off the paper after it cools, roll it up with heavy cream and fruit, and chill in the fridge with the overlap facing downwards.
Cut off the crust, and it is done. Warming up the knife in a direct flame will produce a clean cut.
Story Behind this Recipe
I uploaded this variation of Recipe ID: 2050212 as a different recipe based on the recommendation of a COOKPAD support member. I just planned on introducing it as a simple variation, but it became its own recipe, and I am happy yet embarrassed about it.