Place a washed potato in a pot and add enough cold water to cover the potato by at least an inch. Use high heat to bring the water to a boil. Once the water is boiling, reduce the heat to medium-low and let the potato simmer for about 40 minutes until the potato is soft. Remove the potato from the pot, soak or rinse it under cold water before handling.
Peel the potato. (The potato should weigh about 300g at this moment after it's cooked and peeled.) Use a potato masher (I didn't have one at home, so I used a garlic press) to mash the potato until it's smooth and creamy. Use clean hands to mix 2 cups of potato starch and ¾ cup of cold water into the mashed potato until it forms a smooth dough. If the dough feels too dry, gradually add 1 to 3 tablespoons of cold water until the desired consistency is reached. You can use half of the dough for making potato dumplings: take a portion of dough (approximately 30g) and shape it into a ball (the size of a ping-pong ball). Next, halfway press down on the center of the dough with the top of a water bottle, creating a mushroom shape potato dumpling.
You can use the rest half of the dough for making potato noodles. Take approximately ¼ of the total amount of dough intended for making potato noodles and boil it for 10 minutes or until it floats. Knead the cooked and uncooked dough portions together until they are thoroughly combined. Next, take a portion of the dough (around 50g) and roll it into a ½''-thick long noodle. Repeat this process with the remaining dough until it is all rolled into potato noodles.
Use high heat to bring a large pot of water to a boil. Gently add potato dumplings or potato noodles to the pot. Once the water is boiling again, reduce the heat to medium-low and let the potato dumplings simmer for about 15 minutes (the potato noodles simmer for about 10 minutes) until fully cooked. Drain and transfer to serving plates.
To make the sauce, add minced garlic, sesame seeds, chopped green onions, chopped cilantros, chili powder, peanut butter, granulated sugar, and salt to a heat-resistant bowl. Heat up ¼ cup of vegetable oil in a small saucepan over high heat until it starts to smoke. Carefully pour the hot oil over the sauce ingredients.
Use a spoon stir the sauce ingredients and oil together. Add chicken bouillon, soy sauce, and black vinegar to the sauce mixture. Stir until all the ingredients are well combined. Add the sauce to cooked potato noodles or dumplings, stir until well combined. Serve the dish hot and enjoy.