1. Bring water to a boil. Remove water from heat, then add in shiitakes. Rehydrate for 15 minutes. While you wait, coarsely chop white mushrooms, green onions, lemongrass and cilantro. Reserve both the shiitakes and steep water.
2. In a large pan, sauté the white mushrooms with butter until their water evaporates. season with salt and pepper. Add in the shiitakes, green onions and sesame oil, then cook for 2 more minutes. Add in the steep water and vegetable broth and bring to a boil. Finally, lower heat, add in lemongrass, cilantro, soy sauce, wakame and ginger, and simmer for 20 minutes, stirring occasionally. (Start making lemongrass & cilantro foam while you wait.)
3. Once the soup has reduced a bit, turn off the heat and stir in miso. Filter and discard solids.
4. Place ice cubes in a large bowl and fill with cold water.
5. Bring ¾ of a cup (190 ml) of filtered miso soup to a boil with agar-agar, then remove from heat immediately.
6 Fill a food-grade syringe with the agar-agar preparation. Plug syringe into a silicone tube and fill up the tube, then place it in the ice bath for 1 minute. Remove the tube from the ice bath, then, using the syringe again, push air into the tube to eject the spaghetti. Repeat until enough spaghettis are obtained.
Lemongrass & Cilantro Foam
7. Bring water to a boil. While you wait, coarsely chop cilantro and lemongrass. Remove boiling water from heat and infuse cilantro and lemongrass for 10 minutes. Add in lime juice and let sit to cool.
8. Transfer cooled infusion to a rectangular, flat-bottomed bowl. Sprinkle in soy lecithin. Using a hand blender, blend for 3 to 4 minutes, then let sit for 5 minutes.
9. To serve, collect foam using a spoon. If needed and to obtain more foam, repeat step 8.
9. Divide the spaghettis between plates and decorate each plate with blue-foot mushrooms, enoki mushrooms and wakame. Serve lemongrass and cilantro foam on the side.