In a large mixing bowl, whisk together the all-purpose flour, glutinous rice flour, sugar, yeast, and salt.

Warm the milk and water to about 110F/43C, then pour into the dry ingredients along with the oil. Stir with a wooden spoon until a sticky dough forms.

Knead the dough in the bowl for 3 to 4 minutes until smooth and elastic. It will be tackier than bread dough, that's normal. Cover with plastic wrap and let rise in a warm spot for 60 minutes, until doubled.

While the dough rises, mix the brown sugar, cinnamon, chopped peanuts, and salt in a small bowl for the filling.

Punch down the dough and divide into 8 pieces, about 65 g each. Oil your hands well so the dough doesn't stick or tear.

Flatten one piece into a 10 cm / 4-inch disk in your palm. Spoon 1 tbsp filling into the center, gather the edges up, and pinch firmly to seal into a smooth ball. Repeat with the remaining dough.

Let the shaped balls rest, seam side down, for 15 to 20 minutes while you heat the pan.

Heat 2 tbsp oil in a 25 cm / 10-inch nonstick skillet over medium heat. Add 3 to 4 dough balls, seam side down, leaving space between them.

Cook for 1 minute until the bottom sets, then press each one flat with an oiled hotteok press or the back of an oiled spatula to about 1 cm / 0.4 inch thick and 10 cm / 4-inch wide.

Fry for 2 to 3 minutes per side, adding more oil as needed, until both sides are deep golden brown and the sugar filling has melted. Work in batches so the pan isn't crowded.

Transfer to a wire rack for 1 minute before serving. The filling stays molten and can burn your tongue if you bite in too fast.