1 butter is softened at room temperature, add fine sugar and salt, and stir evenly with a manual eggbeater or scraper.

Add the egg yolk twice, and then add the next time after each stirring.

3. Add the sieved low flour and stir evenly with spatula to form dough.

4. Add yam mud and stir evenly with a scraper.

5 Take a piece of dough about 20g, knead it round and flatten it, and put it on a baking tray covered with tin foil or baking paper.

6 Middle layer of the oven, 170 degrees, about 20 minutes (keep an eye on it, adjust the baking tray in the middle to make the surface slightly discolored).

7. After cooling, put it in a fresh-keeping box and seal it.