Wash the potatoes, dab dry, possibly cut in half. Cut bacon into pieces. In a frying pan, leave it crispy and put it aside. Add oil to the bacon fat. Fry the potatoes at medium heat, turning occasionally, for about 10 minutes, season with salt.
In the meantime, clean and wash the mushrooms and spring onions. Clean and wash the tomatoes as well, halve them depending on size. Add the mushrooms to the potatoes, fry for another 5 minutes. Season with salt and pepper.
Fry the tomatoes, spring onions and bacon for another 1 minute. Wash the thyme and remove the leaves from the stems. Mix with crème fraîche and serve with the potato pan.