Wash the potatoes well. Place one potato on each piece of aluminum foil, brush all around with olive oil and sprinkle with a little salt. Close the aluminum foil tightly around the individual potatoes, place on a baking sheet and cook in a preheated oven (fan oven approx. 200 ° C) for 30-40 minutes, depending on the size.
In the meantime, mix the ingredients for the sour cream well.
Just before the end of the cooking time, clean the mushrooms and cut in half or quarter, and finely chop the shallot. Melt the butter in a pan and fry the mushrooms and shallot vigorously until liquid comes out of the mushrooms. Season to taste with salt, pepper and parsley.
Remove the aluminum foil, place the potatoes on a plate and cut deeply in the middle. Pour the sour cream into the gap, spread the mushrooms on top.
Grilled meat, garlic baguette and / or salad go well with this.