Melt the yeast into warm water.

Shift the flour into the yeast mixture.

Add the egg,sugar,salt & boiled sweet potatoes and knead it become a dough.

Let the dough rest for 20 minutes.

After dough become double-sized, divide the dough into donuts size that you prefer.

Shape it into ball shaped that press the middle with your finger that make a hole like the donuts.

Deep fry it into hot oil until golden brown and coat with castor sugar after the donuts is cool completely.