1. Separation of egg white and egg yolk
2. Milk and oil mix well
3. Add 10 grams of sugar to the egg yolk and stir well
4. Pour the milk and oil mixture into the egg yolk and stir well
5. Sift into low-gluten flour twice and mix well
6. Add the walnuts and stir. Roast the walnuts at 130°C for 5 minutes, don’t burn them
7. Put the egg whites in vinegar, and the remaining sugar will be split into three times until it is wet and foamy. It can also be dry
8. Scoop 1/3 egg white into egg yolk paste
9. Stir evenly
10. Pour the egg yolk paste into the remaining egg whites and stir evenly
11. Spread greased paper on the baking tray, pour the cake batter into the baking tray and shake out bubbles
12. Preheat the oven in advance, and bake the middle layer at 150°C for 20 minutes
13. Take out the undercut, tear off the grease paper, and let the heat sink for a while
14. When the cake is warm, turn it over and sprinkle the purple sweet potato filling. (Purple potato filling is thinner with milk)
15. Roll it up, put it in the refrigerator and set for 1 hour, then remove and cut into pieces.
Tips:Whisk the egg whites must be done in an oil-free and water-free basin. When you roll it, roll it up tighter. The cakes I made are not too sweet. If you like sweet ones, put more sugar.
