In a saucepan, add a dash of Mirin, a few drops of rice vinegar, and a good slug of sparkling white wine, Prosecco or spumante, preferably sweet. Add soy sauce, then bring to the boil. Wait five minutes till the alcohol and has reduced to your taste. Meanwhile soak the seaweed and shitake mushrooms. Add this soaking water to the stock base (it is rich in mineral salts). Add an additional half a litre of water. Slice the mushrooms and add these too. Mix together with a sachet of powdered ‘dashi’ stock. Add about 1 tablespoon of brown sugar. Wait till it comes to the boil. Then add the seaweed and bean sprouts and boil for five or 10 minutes. While the stock boils, cook the soba noodles separately in salted water. Once cooked, drain them and put in a bowl of cold water. Prepare the tempura as per our basic recipe. Now assemble the dish: take a large bowl, drain the soba and put them into the bowl. Pour over a ladle of soup and lay on top two pieces of lovely hot tempura. Serve the rest of tempura in a side bowl.