Prepare the mushrooms. Place the mushrooms in a large saucepan and cover with water. Place over high heat and bring to a boil. Add salt. Reduce heat to low and cook the mushrooms for 20 minutes. Drain the cooked mushrooms in a colander to drain the water. Then mince them into a clean bowl. Pour half the vegetable oil into a deep frying pan and add the mushrooms. Place over medium heat. Fry, stirring, for 10 minutes.
Prepare the sauté. In another frying pan, fry the onion and carrot for 5 minutes over medium heat. The vegetables should become soft. Mix the vegetables and mushrooms in one frying pan. Simmer under a lid for 3 minutes over low heat. Arrange the caviar in jars. Do not cover with lids. Place in the oven for 2 hours to complete the cooking and sterilization. Place the jars in a cold oven, preheat it to 120 ˚C. After 2 hours, remove the jars from the oven and roll up immediately. After rolling up, turn the jars upside down. Cover with a blanket and leave until completely cool.