Preheat the oven to 200 ° C. Peel the potatoes and cut into pieces. Put in a dripping pan, season and drizzle with oil. Sprinkle with rosemary needles and cook in the oven for about 30 minutes.
Then spread the zucchini and mushrooms cut into small pieces. Cook for another 15 minutes. Add the tomatoes and the broth to the vegetables, continue cooking for about 5 minutes, season with salt and pepper.
Finely chop the basil, mix with sour cream and yoghurt, season with salt and pepper. Serve separately with the oven vegetables.