About 1 cup (235 milliliters) vegetable oil or any neutral flavored oil, for frying
For the dough: In a small saucepan, warm the milk up slightly and whisk in the sugar and yeast making sure they are dissolved completely. Let stand in a warm place to activate until bubbly, 3 to 5 minutes.
In a large bowl combine the salt and all three of the flours. Slowly pour in the warm milk and yeast mixture. Mix gently with a wooden spoon until a uniform, but slightly sticky dough forms. Shape into a ball and cover the bowl with a damp cloth. Let rise in a warm place, until doubled in size, 1 1/2 to 2 hours.
Knock the dough down and let rise again until doubled in size, another 1 1/2 hours.
For the filling: In a small bowl, mix together the muscovado sugar, peanuts, cinnamon and salt.
After the dough has risen the second time, dust a clean surface with flour and knock the dough out on to it. Dust the top of the dough with some more flour and knead a couple of times. Shape the dough into a fat long log. Divide the dough into 10 even pieces and shape into balls (about 75 grams/2.6 ounces each). Cover with plastic wrap. Dusting with flour as necessary to prevent sticking, press a dough ball into a 4 inches/10 centimeters in diameter round disk using your fingertips. Place the disk in your hand and cup it slightly. Scoop in about 1 1/2 to 2 tablespoons of the sugar mixture into the center of the disk. Seal closed by pinching the edges together at the top wrapping the dough around the filling. Once sealed, reshape gently making a round ball. Set down with the seam side down on a well-floured surface. Cover with plastic wrap. Repeat forming the pancakes with the remaining dough and filling.
Place a large nonstick skillet over medium-high heat and coat generously with oil, 3 to 4 tablespoons. Working in batches of 3, place the pancakes seam-side down on the frying pan and immediately flatten them gently with a spatula. Fry over medium to medium-low heat until the dough is golden crispy brown and slightly springy to the touch, 3 to 4 minutes on each side. Transfer to a wire rack as done. Wipe your pan clean with a paper towel in between batches and use fresh oil with each batch. Let the pancakes cool slightly before eating. Be careful not to burn yourself in your haste to gobble these up as the insides are hot and oozing.
These are great with a scoop of vanilla ice cream and/or whipped cream on top for an extra treat. When shaping, make sure your dough disks are even in thickness. This will ensure that your hotteok will have filling from edge to edge. If you can't find muscovado sugar, substitute dark brown sugar. I found that muscovado melts the best to get that oozing center result.