Let's cook.
In a medium bowl, whisk together the all-purpose flour, sugar, instant yeast, and salt.
Gradually add the warm water to the dry ingredients, mixing with a spoon or spatula until a shaggy dough forms. Cover the bowl with plastic wrap and let it rest in a warm place for 30 minutes to 1 hour, or until slightly puffy.
Divide the dough into 4 equal portions. Lightly oil your hands to prevent sticking.
Flatten one portion of dough into a small disc in your palm. Place about 2 tablespoons of sweet red bean paste in the center. Carefully gather the edges of the dough to seal the filling inside, forming a ball.
Heat 1 tablespoon of vegetable oil in a non-stick skillet over medium-low heat. Place two dough balls seam-side down in the skillet.
Cook for 1-2 minutes until the bottom is lightly golden. Using a spatula or a hotteok press, gently press down on each pancake to flatten it to about 1/2-inch thick.
Continue cooking for another 2-3 minutes per side, or until both sides are golden brown and the pancake is cooked through. Repeat with the remaining dough balls, adding more oil as needed.
Serve the Hotteok immediately while warm and the filling is gooey.
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