Make the dough. Combine 1 cup warm milk with 1 tablespoon sugar and 1 ½ teaspoon active dry yeast and let sit for 10 minutes or until the mixture is foamy. Mix the yeast mixture with 1 ¾ cup flour, ½ cup sweet rice flour, ½ teaspoon salt, and 1 tablespoon olive oil until well combined. Knead the dough for about 6-8 minutes or until the dough is smooth and soft. Transfer the dough to a clean bowl, wrap in plastic wrap and let proof for 1 hour in a warm area or until doubled in size.
Meanwhile, make the pumpkin filling. Mix together ½ cup pumpkin puree with ½ cup brown sugar, 1 teaspoon cinnamon, and ¼ cup chopped toasted walnuts. Set aside.
Punch down the dough, cover, and let rest for 20 minutes.
Divide the dough into 8 equal portions. Shape each portion to a ball and roll into a 6-7 inch circle. Place about 2 tablespoon of the filling in the center and gather the edges to enclose the filling. Flatten the hotteok to make a round disc. Repeat with the remaining portions.
Heat ¼ cup oil in a saute pan over medium heat. Fry the hottoek in the hot oil, cooking 2-3 at a time. Slightly flatten the pancakes with a spatula. Flip the pancakes once golden brown and cook the other side. Remove the hotteok and drain the excess oil on paper towels. Repeat with the remaining portions, adding more oil as needed. Serve warm.