Prepare the Udon noodle broth - Pour boiling water over your dried shiitake mushroom, enough to cover and steep for about 30 minutes to allow to soften. Do NOT throw away the shiitake broth as this will be used in the soup broth. Remove the stems from shiitake mushrooms and slice thinly to use as a garnish for your soup. Set aside.
In a pot add your shiitake mushroom broth, water, dashi (if making vegan gluten free vegetable broth), mirin, tamari (soy) sauce and salt to taste over medium heat for about 10 minutes – keep warm. Skim the film off the top of the soup.
Boil your udon noodles in salted water for 2-3 minutes per package instructions and then rinse with cool water and set aside.
Prepare your shrimp- Peel your shrimp but leave on the tail. Remove the black/white vein from the back of the shrimp by running your knife along the back of the shrimp just and pull out the vein and discard. Lay your shrimp on its side and scrape any remove the black from the tail of the shrimp.
Make the shrimp long and flat - Lay the shrimp belly side up and make several horizontal slits about 1/8 apart only about half way through the shrimp. Be very careful to not cut all the way through. Then take the shrimp and flip over so the back side is up on top and lay flat on your working surface. Take your thumb and your pointer and middle finger and press down slightly to make flat. You will hear a slight crunch and that is exactly the effect you are going for. You want to break down the proteins so they lay flat and stay flat and long during the cooking process. Rinse the shrimps and dry extra good with a paper towel. You need to get the shrimp EXTRA dry!
Add cooking oil to your cooking vessel of choice. You need to make sure that the oil is at least 2 inches deep. Preheating your cooking oil to about 180 degrees C (360 degrees F). Your oil should sizzle when you put in a little bit of the tempura batter. Your oil should not be so hot that it is smoking.
In the meantime, prepare your tempura shrimp assembly line. Place ½ cup potato starch or cornstarch in one plate and set aside. Prepare your tempura batter. In a medium bowl add the other ½ cup of potato starch, ½ cup cake flour/00 flour (if need to be gluten free, try rice flour), 1 beaten egg and 1 cup extra cold seltzer water or just regular water. Mix, so very gently just to combine the big lumps but essentially it should be very lumpy and just barely combined and then it is perfect. Get this tempura batter on top of a larger bowl filled with ice to keep it cold. (if your batter gets warm it activated the glutens and this results in a tough batter and you want yours to light and crispy) You should now have in front of you your prepared shrimp, a plate of potato/corn starch for dusting, prepared tempura batter sitting over a bowl of ice and ready to go hot oil in your pan for frying.
Double check your oil to make sure it is ready to go. Place a little bit of the prepared tempura batter into your frying pan and if it sizzles you are ready to go.
Dip your shrimp into the potato starch/ corn starch to dust on all side and shake off the excess. Next dip your shrimp into the wet tempura batter on all sides and then slowly and carefully place your shrimp into the hot oil for frying. Fry the shrimp for about 1 to 1.5 minutes. You will know when your shrimp are done because then you pick up the shrimp they will be crispy on all side and the shrimp will stay firm and will not limp. If your oil is not hot enough, you will end up with a soggy shrimp and if the oil is too hot your shrimp will be tough. Remember you are looking for a 180 degrees C (360 degrees F) oil and your shrimp should sizzle aggressively when placed in the oil.
Remove the shrimp on to a plate lined with paper towels to drain and season with salt to taste.
Serving up your Shrimp Tempura Udon Noodle bowls. Place your cooked udon noodles into a serving bowl, ladle over the hot broth, garnish with sliced shitake mushrooms, sliced green onions and shrimp tempura.
We like to make extra shrimp tempura on the side and we serve with our dipping sauce. Mix water, dashi, tamari, mirin and grated daikon. Dip the prepared tempura shrimp into the dipping sauce and enjoy!