Mentha × piperita
Plate from Flore médicale, Paris, 1833–1835. Biodiversity Heritage Library, no known copyright restrictions.
Nearly impossible to kill, and just as hard to contain — grow it in a pot unless you want it everywhere.
It likes damp soil and doesn’t mind some shade. Cut it hard and it comes back thicker.
Fresh leaves, lightly crushed, over hot water. A cup after dinner settles things nicely.