Wrap the tofu with paper towels, a muslin cloth, or a cheesecloth. Place the tofu on a plate and place a weighted object (like a bowl) over the wrapped tofu. Be careful that what you place on top won’t tip over as you press the tofu. Press the tofu for 15 to 20 minutes. Then, use your hands to crumble the tofu into a bowl.

Heat 1 1/2 tablespoons of canola oil in a sauté pan over medium-high heat. Add the chopped mushrooms and cook for about 2 to 3 minutes, until the mushrooms start to shrink. Season the mushrooms with a small pinch of kosher salt. Transfer the mushrooms to the bowl with the tofu. 

Add all of the other ingredients for the filling to the bowl and mix together. Some gochujang is spicier than others, so you may want to only use 2 tablespoons instead of 3. Set the filling aside.

Mix the potato starch, tapioca flour, and kosher salt in a bowl. 

Bring 1 1/2 cups of water to boil into a saucepan. Measure 150 grams or 2/3 cup boiling hot water and pour it into the bowl with the flours. I usually pour 150 grams of hot water directly into the bowl. Cover the saucepan with the lid and set it aside. You may need the water again if the dough is feeling dry. 

Stir the flour and water together for about 1 minute. By now, most of the loose flour should be gathered into small bits of dough. Drizzle 1 1/2 teaspoons of oil over the dough. 

Use your hands to start gathering and kneading the dough together. If the dough is too hot to touch, cover it with a lid and let the dough rest for 2 minutes before kneading. The dough should come together pretty easily. If the dough feels very dry even after 1 minute of kneading the dough, drizzle 1 tablespoon of the reserved hot water over the flour and knead. Continue doing this until you’ve gathered up all the bits of dough into one large lump of dough.

Transfer the dough onto a counter or surface and knead the dough for another 2 to 3 minutes, until it is nice and smooth. You don’t need to flour the surface. The dough will feel moist but shouldn’t be overly sticky after 2 minutes of kneading. If it is feeling sticky, sprinkle some potato starch over the dough and knead it into the dough. 

While you still have warm water on hand, make the dipping sauce. In a small bowl, combine 1 tablespoon of warm water with 1 1/2 teaspoons sugar until the sugar fully dissolves. 

Mix in the rest of the ingredients for the dipping sauce. Set the sauce aside. 

Cut off the zipper portion of a quart-size plastic ziploc bag. Then, cut open 2 sides of the plastic bag. The bag should now open and close like a folder. (See note 3)

Divide the dough in half, and transfer 1 piece of dough back into the mixing bowl and cover it with a lid or damp towel. 

Cut the other half of dough into 12 equal pieces, about 13 to 15 grams each. Roll the pieces into small balls. Place all the small balls of dough except 1 into the bowl with the large dough half. Keep the bowl covered. Alternatively, you can leave the small balls of dough on your counter and cover them with plastic wrap to prevent them from drying.

Open up the ziploc bag. Place one ball of dough in the center. Cover the dough with the other side of the ziploc bag. Use the palm of your hand to flatten the dough into a disc. Using a rolling pin, roll out the dough like pie crust until the dough is about 2 to 3 inches in diameter. Then, place the rolling pin over the center of the wrapper. Press and push the dough outward in a sweeping motion, until the dumpling skin is about 3.75 inches in diameter. 

Uncover the dumpling skin and place it on one hand. Place about 2 teaspoons of filling on the center of the skin. Pinch together the skin on the right. Using your index fingers, create a pleat and seal it over to the right. Continue making pleats and seal them over to the right until you have finished making the dumpling. (See note 4) 

Transfer the dumpling to a pan or bamboo steamer lined with parchment paper. Cover the pan or bamboo steamer with a towel to keep the dumplings from drying out.

Continue making the dumplings until you’re out of dumpling dough. You’ll likely have a lot of filling leftover, so use it in a stir fry.

Fill a large wok with water and place a steaming rack in the center. Make sure that the water level is below the top of the steaming rack (by about 1/4 to 1/2 inch). Bring the water to boil.

Carefully place one of the plates with the dumplings onto the steaming rack and cover the wok with the lid. Steam the dumplings for 5 to 6 minutes. Then, steam the rest of the dumplings.

The dumpling skin is a bit chewy in texture. I recommend pan frying them in oil over medium-high heat for about 4 minutes to blister the bottoms. Make sure to do this in a nonstick pan to prevent the dumplings from sticking to the pan.

Serve the dumplings immediately. 

Freezer Directions: Line pleated dumplings on plates or pans lined with parchment paper. Make sure the dumplings aren’t sticking together or else they’ll be tough to break apart. Once the dumplings harden, transfer them to freezer bags. The dumplings will have minor cracks once they’re frozen. Don’t worry, the cracks will seal up during the steaming process. You do not need to defrost the dumplings before cooking. Just steam them on high heat for 7 to 8 minutes.