Preheat the oven to 200°C (392°F).
Wash the baby potatoes thoroughly and place them in a pot. Cover with water and cook for about twenty minutes until tender but still firm.
Check the potatoes by inserting a skewer, it should slide in easily.
Drain the potatoes in a colander. Clean the button mushrooms carefully and drain them well.
In an ovenproof dish, combine all the ingredients with the baby potatoes and mushrooms. You can cut some of the potatoes in half.
Mix everything well to ensure the vegetables are well coated with the marinade. Place a few sprigs of fresh thyme and rosemary on top.
Bake for about 15 minutes until the mushrooms are cooked and the baby potatoes have a nice golden color.
Serve hot as a side dish with meat.