This versatile, vinegar-seasoned mushroom marinade is perfect for all kinds of button mushrooms, oyster mushrooms, or wild mushrooms. It keeps for weeks in the refrigerator, but can also be enjoyed immediately in salads, with roasts, or on warm toast.
… Ingredients (for approx. 500 g mushrooms)

Mushrooms: 500 g small mushrooms (or larger ones, halved/quartered)
Pickling liquid:

300 ml water
100 ml 10% vinegar (or apple cider vinegar for a milder flavor)
3 tbsp olive oil
1 heaped tbsp salt
1 tbsp sugar

Spices:

3 garlic cloves (thinly sliced)
10–12 black peppercorns
1 bay leaf
1 tsp thyme (fresh or dried)
1 tsp mustard seeds
Preparation step by step

Prepare the mushrooms: Clean the mushrooms (do not soak, just wipe or rinse briefly). Leave the small seeds in.

Prepare the marinade: Mix the water, vinegar, olive oil, salt, sugar, and all the spices (including the garlic) in a pot. Bring to a boil.

Cooking: Add the mushrooms to the boiling marinade and cook over low heat for 6–8 minutes. The mushrooms will shrink slightly and absorb the spices.

Portioning: Place the mushrooms and spices in sterilized jars and pour the hot marinade over them until they are completely covered.

Consumption and Storage: Seal the jar. Allow to cool to room temperature and then refrigerate.

Tastes great after just 12 hours, but develops its full flavor after 2–3 days!