Start preparing the caviar. Pour water into a saucepan with mushrooms. Put on high heat and bring to a boil. Reduce heat to low and cook mushrooms for 20 minutes. Throw the boiled mushrooms into a colander and leave for 10 minutes to drain. Pass through a meat grinder into a clean bowl.
Fry the onion. Pour 3 tablespoons of vegetable oil into a deep frying pan. Put on medium heat and add the onion. Fry, stirring, for 3-4 minutes. Add the carrots and stir. Fry for another 4 minutes.
Add tomatoes. Pass the tomatoes through a meat grinder into a bowl with mushrooms. Add salt, pepper and the remaining vegetable oil. Put the fried carrots and onions into the same bowl. Mix the ingredients well.
Make mushroom caviar. Place the resulting mass in a clean deep frying pan. Put on low heat and cover with a lid. Cook for 50 minutes. Put the finished caviar in a clean dry jar and put it in the refrigerator.