1. Weigh out the oil and milk and put them in a small basin
2. Stir evenly with a manual whisk
3. Sift low-gluten flour, cornstarch and cocoa powder at one time, and stir evenly with a spatula
4. Share the egg whites and egg yolks, put the egg whites in a clean oil- and water-free basin, put the egg yolks in the roux, and stir evenly with a spatula
5. Add a pinch of salt to the egg white, add granulated sugar in three times, beat until moist and foamy
6. Take a part of the egg white and put it in the egg yolk paste, stir evenly with a spatula
7. Pour back into the egg white basin, stir evenly, preheat the oven to 180 degrees
8. Pour the batter into a baking pan lined with greased paper
9. Smooth it, put it in the middle and lower layer of the oven, and bake for about 20 minutes. After it is out of the oven, remove the low oil and put it on the grill to cool down
10. Whip the whipped cream, harden the cream, take out an appropriate amount of cream with a spatula, put it on the cake, and smooth it
11. Use a rolling dough stick to help roll up the cake roll
12. Wrap it in oil paper, roll it tightly, and put it in the refrigerator for at least half an hour to shape
13. Put the chocolate and milk in a bowl, and the insulated water will melt
14. Take out the cake roll, tear off the oily paper, pour the chocolate melt on the cake roll, spread it evenly with a spatula,
15. After the chocolate is half-solidified, use a small fork to draw lines from the left side to the right side of the cake roll
16. Put it in the refrigerator freezer to accelerate the solidification of the chocolate, then you can eat it
