Ingredients:
- 210g russet potatoes
- 60g plain flour
- 200g purple sweet potato
- Sugar (optional, to taste)

Instructions:
1. Peel the russet and purple sweet potatoes. Steam them until soft.

2. Mash the steamed russet potatoes into a paste. Add flour and mix. Wear gloves to prevent sticking. Knead into a dough and divide into 6 portions.

3. Add sugar (if using) to the purple sweet potato and mash into a paste. Divide into 6 portions.

4. Take a piece of dough and flatten it. Place a portion of purple potato in the center. Pinch the dough tightly around the filling and flatten it into a patty.

5. Grease a frying pan with a thin layer of oil. Fry the patties on low heat until both sides are golden brown.