Place potatoes in boiling water and cook until tender.
Heat a frying pan with vegetable oil. Chop the onion finely. Cut the champignons into random pieces. Fry the onion and champignons in a frying pan for 7-9 minutes over medium heat until done. Then remove from heat.
Drain the water from the potatoes, peel them and put them in a deep bowl or saucepan. Add salt and pepper to taste. Mash with a masher or fork.
Add fried mushrooms with onions and finely chopped herbs to the potatoes.
Mix the puree with the mushrooms and herbs.