Bring vinegar, 200 ml water, sugar, bay leaf and spices to the boil until the sugar is dissolved. Stir in Aquavit and let the brew cool down.
Peel onions and cut them into thin rings. Rinse the maties cold, dab dry and cut into pieces about 3 cm wide. Divide the maties and onion rings into one large or two small preserving jars.
Cover with the stock. Close the glasses well and let them steep in the refrigerator for at least 2 days. Tastes good on brown bread and with boiled potatoes.