Defrost frozen mushrooms on kitchen paper. Allow dried mushrooms to swell in 800 ml of hot water for about 15 minutes. Peel and finely dice onions. Heat 2 tbsp. butter in a pot. Fry the onions in it until transparent.
Pour the wine. Add soaked mushrooms together with soaking water and bring to the boil. Stir in broth and simmer covered for about 20 minutes. Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer).
In the meantime, line a baking tray with baking paper. Finely grate the Parmesan cheese. Wash parsley, shake dry, pluck off leaves and chop. Mix with parmesan, up to 1 tablespoon. Sprinkle about 12 small oval cookies onto the baking paper and press them flat a little.
Bake in the oven for 8-10 minutes. Let it cool down on the baking paper.
In the meantime defrosted mushrooms dab dry well and cut in half. Clean the mushrooms, wash them briefly if necessary and halve them. Heat oil and 2 tablespoons of butter in a pan. Fry the mushrooms for 3-4 minutes while turning them.
Season with salt and pepper.
Puree the mushroom soup finely with a hand blender and possibly pour through a fine sieve. Refine soup with cream. Season with salt, pepper and 1 pinch of sugar. Heat the mushrooms in the soup. Shortly before serving, warm milk in a high pot (approx. 70 °C), but do not boil.
Season with a little salt and foam up with a hand blender. Spread immediately on the soup. Garnish with parmesan chips and parsley.