Sweet pancakes with brown sugar syrup filling (Hotteok)

Steps

1. Place 1 cup of lukewarm water into a mixing bowl. Add white sugar, yeast, kosher salt, vegetable oil, and stir it well. Add 2 cups all purpose flour and mix it with a rice scoop, or by hand. Let the dough rise. It should sit with the lid closed at room temperature for 1 hour. After an hour the dough will rise to double its size. Knead it to remove the gas bubbles in the dough. Let it rise for another 10-20 minutes.
2. Mix the turbinado sugar, cinnamon powder, and walnuts in a bowl.
3. Knead the dough again to remove the gas bubbles. Place and spread about ½ cup flour on your cutting board. Put the dough on your cutting board and knead it. Make it into a lump, and cut it into 8 equal-sized balls. Take 1 dough ball, flatten it, put some filling in the center of the dough, and then seal it to make a ball. Repeat this 8 times to make 8 stuffed balls.
4. Place 1 ball on the pan and let it cook for 30 seconds. When the bottom of the dough ball is light golden brown, turn it over and press the dough with a spatula to make a thin and wide circle (about the size of a CD). Let it cook about 1 minute until the bottom is golden brown. Turn it over again and turn down the heat very low. Place the lid on the pan and cook 1 more minute. The brown sugar filling mixture will be melted to syrup! Serve hot!