To make the batter, whisk together flour, salt, mushrooms seasoning, pepper with water in a bowl until all incorporated.
Chop the mushrooms and carrots into tiny bits, separately.
Peel off the daikon's skin and shred using a box grater (used the large hole).
Heat a large non-stick pan with a tablespoon of oil over medium heat. Sauté mushrooms until they turn slightly golden and aromatic, about 2-3 minutes. Then, add the carrot and cook for another 45 seconds or so.
Add the daikon and continue to cook until it turns translucent and all water has evaporated (See Notes). Season with salt, sugar, and pepper (if using).
Turn heat to low, give the batter a good stir and add to the daikon mixture.
Then continue to cook while stirring constantly until the mixture thickens. The mixture should look like a thick paste.
Transfer the mixture into a lightly greased 9X5 non-stick loaf pan pressing gently into the pan with the back of the spatula to remove as many air bubbles as possible. Then, cover it with foil, if needed, or cover the steamer's lid with a towel (see video).
Steam the cake over high heat for about 30-40 minutes (make sure you have enough water in the steamer). It's normal to have a thin layer of water on the top when you uncover the lid.
Let the cake cool down completely/refrigerate overnight. (Note: This savory cake can be served right after steaming - the texture will be soft.)