Peel the potatoes, put them in a saucepan, cover with cold water, add salt, and let stand for 20 minutes. Wash the champignons and dry with a paper towel. Remove the top layer of skin from the mushroom cap, remove any discoloration, and recut the stem of the mushroom.
Remove the potatoes from the water, dry and cut into thin slices.
Cut the mushrooms into thin slices.
Heat a frying pan with a piece of butter. Fry the potatoes, turning, for 10 to 12 minutes, until they are golden and have an obvious crust.
Heat another frying pan with a knob of butter and fry the mushrooms for 5 minutes.
Add the mushrooms to the potatoes in the pan, add salt and pepper, stir and fry for another 3-5 minutes. The dish is ready.
Serve the fried potatoes hot, garnished with finely chopped fresh herbs.