Rinse 2.5 cups of rice (short-grain or medium-grain rice, such as sushi rice, 535 g / 1.17 lb) under cold water until the water runs clear. Transfer the rice to a medium bowl and add enough water to fully submerge it. Cover and soak for about 12 hours or overnight.
Drain the rice well and let it sit in a fine-mesh strainer at room temperature for about 1 hour to remove excess surface moisture. For reference, the soaked rice will weigh roughly 697 g (1.53 lb) once fully hydrated.
Grind the rice in a powerful food processor until it becomes a fine, flour-like powder. If needed, work in batches so the rice grinds more evenly. Stop periodically to scrape down the sides and redistribute the rice so it grinds evenly.
Sift the rice flour into a clean bowl in two or three batches, as it sifts more easily in smaller quantities. Remove any clumps or unground rice grains. Once all the flour has been sifted, sift it one more time to ensure it is very fine.If you find a noticeable amount of unground rice, return it to the food processor and grind it again, then sift once more. In our testing, we ran the rice through the grinder more than once to achieve an extra-fine texture. This step is important for smooth garaetteok, as insufficiently fine flour can result in gritty rice cakes.You should end up with about 4.5 cups of fine rice flour.
HOW TO MAKE RICE CAKE WITH A MICROWAVE
Combine the rice flour, cornstarch, fine salt, and 1/4 cup of boiling water in a microwave-safe bowl. Mix well. Add another 1/4 cup of boiling water and mix again until smooth. The mixture should be easy to stir, not stiff like cookie dough.
Cover the bowl with cling wrap, leaving a small gap for steam to escape. Microwave on high for 2 minutes (based on a 1250 W microwave).
Carefully remove the bowl, add another 1/4 cup of boiling water, and mix well. Cover again and microwave on high for a further 1 minute 30 seconds. Remove from the microwave.
Line a cutting board with a silicone baking mat or several layers of cling wrap to prevent sticking. Carefully transfer the hot rice cake dough onto the prepared surface.
Put on thick cotton gloves first, then food-safe gloves over them, as the dough will be very hot. Alternatively, you can use a single pair of thick, heat-resistant, food-safe gloves if you have them. Knead the dough, then pound it with a pestle for about 5 minutes until smooth and elastic.
HOW TO MAKE RICE CAKE WITH A STEAMER
Divide the rice cake dough evenly into 5 pieces.
Line the steamer with a silicone steaming mat (recommended), baking paper with a few holes poked in to allow steam to pass through, or a clean tea towel. Spread the rice flour mixture evenly over the liner, breaking it up into smaller pieces rather than leaving it as one solid mass. This helps it cook through more quickly and evenly. Cover and steam over high heat for 15 minutes.
Line a cutting board with a silicone baking mat or several layers of cling wrap to prevent sticking while shaping the rice cake. Place the steamed rice cake dough on the mat.
Put on thick cotton gloves first, then food-safe gloves over them, as the dough will be very hot. Alternatively, you can use a single pair of thick, heat-resistant, food-safe gloves if you have them. Knead the dough, then pound it with a pestle for about 5 minutes until smooth and elastic.
PREPARE RICE CAKE FOR TTEOKBOKKI (SPICY RICE CAKE)
Divide the rice cake dough evenly into 5 pieces.
Lightly coat your palms with about 1/2 teaspoon of sesame oil and gently rub it over the rice cake pieces to prevent sticking.
Roll each piece into a cylinder about 1 to 1.5 cm (0.4 to 0.6 inch) in diameter. Trim the ends, then cut the cylinders into 6 cm (about 2.5 inch) lengths, roughly the size of a little finger. The rice cakes are now ready to use in tteokbokki or other stir-fry dishes.
PREPARE RICE CAKE FOR TTEOKGUK (KOREAN RICE CAKE SOUP)
Divide the rice cake dough evenly into 2 pieces.
Lightly coat your palms with about 1/2 teaspoon of sesame oil and gently rub it over the rice cake pieces to prevent sticking. Roll each piece into a cylinder about 2 to 3 cm (0.8 to 1.2 inch) in diameter.
Place the rice cakes on a large plate, cover with cling wrap, and refrigerate for about 1 hour until firm, which makes them easier to slice. Slice thinly (about 0.5 cm / 0.2 inch thick) on a diagonal into oval shapes. If you’re short on time, you can slice them soon after shaping, but chilling is recommended for cleaner cuts. The rice cakes are now ready to use in tteokguk.
Notes
1 Tbsp = 15 ml, 1 cup = 250 ml
The amounts of water used above are based on homemade rice flour, which is wet-milled. Wet-milled rice flour is more moist than dry-milled rice flour, requiring less water for this recipe. If you are unable to find wet-milled rice flour from your grocer, I suggest you make your own following the instructions above. It's very easy to make at home!
The above ingredients will result in about 450g (1 pound) rice cake.
Cooking time above only accounts for making rice cake using a microwave. It doesn't count for making the rice flour from scratch.
Lots of helpful tips are mentioned in the main post above. Be sure to read them before you make garaetteok to increase your chance of success.