1. Cut the sweet potatoes into thin slices, put them in a steamer, steam them and put them in a bag, roll them into a delicate sweet potato mash with a rolling pin
2. Squeeze the condensed milk into the sweet potato mash, mix well and set aside
3. Pour milk and vegetable oil into the bowl, stir until no oily flowers are visible, then sift the low-gluten flour, and stir evenly with a zigzag technique
4. Prepare the eggs. The egg white and egg yolk need to be separated. The container containing the egg white should be oil-free and water-free. Pour the egg yolk into the batter and stir evenly with a zigzag technique.
5. Beat the egg whites. Add white sugar in three times, add it for the first time when it has a fish-eye shape, add it for the second time when the bubbles are more delicate, add it for the third time when you see the lines, until the whisk is lifted and a small hook appears. can.
6. Scoop 1/3 of the egg whites into the egg yolk paste, mix it evenly with a mixing method, and then pour it back into the meringue, and mix it evenly with the same method of mixing or drawing a zigzag.
7. Pour the batter into the baking pan. The baking pan I used is 28 by 28. The surface layer is smooth, and the batter is gently shaken to remove the bubbles inside.
8. Put it into the preheated oven, bake at 165 degrees for 28 minutes
9. After the cake slices are baked, let them cool, then remove the grease paper and spread the mashed sweet potatoes. Try not to smear the seal of the cake slice to avoid overflow
10. Cut the edge part into an oblique knife for easy closing
11. Use a rolling pin to lift up the non-stick paper and gently roll it up, then turn it around to roll the cake into the greased paper and let it sit for four hours to set the shape
12. After cutting open, you can use mashed potatoes to make a decoration, with a perfect appearance