Pear the fennel seeds in a mortar just before preparing the tea. Pour 1 1/2 liters of boiling water over all ingredients, put the lid on and let it stand for 10 minutes. Let the condensation water (= essential oils) drip back into the jug. Sieving. If necessary, refine with a little honey or lemon, depending on your taste. Immediately fill the thermos with hot water to take away.
Does good, in summer as in winter, suitable for outdoor activities.
I got the recipe from the grandmother of a school friend; she knew what was good.