1. DASHI: Dashi is stock made of dried kelp (kombu) and bonito flakes. Both can be found in any Japanese or Korean market. Use chicken or veggie stock if you don't have dashi on hand. If using commercial ones, keep in mind that different brands have different levels of sodium. Adjust salt and soy sauce accordingly.
To make dashi:
2 cups water
½ oz kombu
¼ cup packed bonito flakes
Place kombu in water and bring to boil in a saucepan over medium heat. Remove kombu just before water boils and when you start to see bubbles around the sides of the saucepan (Broth will turn sticky and bitter if kombu is in boiling water). Add the bonito flakes and turn the heat to medium high. Let it come to a boil. Once boiled, let it simmer for one minute, turn off the heat and let steep covered for 5 minutes. Strain and use. You can make a second round of dashi (lighter flavor) using the same kombu and bonito flakes to not waste them.
2. Nagaimo is a type of Japanese yam that can be found in most Chinese, Korean or Japanese markets. I actually found them sold in Ralphs (believe it or not). It's white/light yellow in color. Some people may be sensitive to raw nagaimo so take head when grating it. Nagaimo adds a sticky, uncooked like texture to the pancake. Start with 2 tbs or less for this recipe if you're not sure you're going to like the texture. If you love it, increase to 4 or even 8 tablespoons for this recipe. If you have access nagaimo, you can use it like a potato. Add to stir fries, curries or even soups. Due to its sticky properties, nagaimo is very good for stomach issues like gerd or gastric.
3. If you can't find Japanese mayonnaise, replace it with regular mayo. For every ¼ cup regular mayo, add ½ tbs rice vinegar and 1 tsp sugar.
4. The type of vegetables used is up to you. You can even add meat or shrimp if you like.