Russian Pan-Fried Potatoes with Wild Mushrooms

medium-sized yellow potatoes

vegetable oil

medium sized onion

or 10.5 oz fresh wild mushrooms (washed and cut into bite-sized pieces (or 30 grams/1 oz dried, see notes below))

garlic (minced)

sprigs thyme (chopped)

freshly chopped parsley + more to garnish

salt and freshly ground black pepper (to taste)

sour cream (to garnish)