Peel the garlic cloves. Wash the thyme. Bring vinegar, 1/2 litre water, sugar, spices and garlic to the boil, cover and cook over a low heat for about 10 minutes. Peel the shallots. Clean, wash and cut the peppers into strips.
Wash and clean the mushrooms and dab dry with kitchen paper. Blanch the vegetables separately in portions in the stock (shallots for about 5 minutes, peppers for about 4 minutes, mushrooms for about 2-3 minutes). Layer the vegetables in prepared glasses.
Pour the boiling-hot stock over it, so that it stands about finger-wide over the vegetables. Close the jars with preserving cellophane and rubber rings. Store in a cool and dark place.