Make the dough

• Warm the milk slightly and stir in the yeast and sugar until dissolved.
• Combine the all-purpose flour, glutinous rice flour and salt in a bowl, then pour in the milk mixture and the vegetable oil.
• Mix into a soft dough, cover and let rise until doubled in size.

Prepare the potato filling

• Boil the peeled potatoes in salted water until tender, then drain.
• Mash the potatoes while still hot and season lightly with salt.
• Let the mashed potato cool slightly, then fold in the shredded mozzarella and cheddar.

Shape the hotteok

• Punch down the risen dough and divide it into equal portions.
• Flatten each portion in your oiled hand, place a spoonful of the potato cheese filling in the center and pinch the edges closed.
• Gently press each ball flat into a disc.

Pan-fry the hotteok

• Heat a generous amount of oil and a little butter in a frying pan over medium heat.
• Fry the discs on each side until golden and crisp and the cheese is melted.
• Drain briefly on paper and serve hot.