Clean, wash and slice the zucchini (possibly with a colored knife). Rinse the thyme and pluck the leaves
Bring vinegar essence, 700 ml water, sugar and salt to the boil. Let the brew boil down for 5-6 minutes
Fill zucchini, thyme and mustard seeds into prepared glasses up to approx. 2 cm below the rim. Cover with boiling hot stock, close tightly. Leave to stand for at least 2-3 days