One of the first perennial food plants I ever tried growing was a herb called lovage (Levisticum officinale). It has an amazing flavour: sort of earthy, yeasty and slightly celery. The drawback is that it grows into an 8ft tall triffid, whereas all it takes is a tiny fragment of leaf to flavour a dish.
The solution is to grow a related plant called Scots lovage (Ligusticum scoticum). It grows wild on the beaches up here and I have fond memories of adding it, freshly picked, to salads and pasta sauces on canoeing trips on the Sutherland coast. If you can’t be bothered going down to the beach every time you want a little bit, it grows modestly and unfussily in a sunny part of the forest garden. It is milder and sweeter than lovage too, so much so that the early leaves are great chopped into spring salads. Cooked, it combines beautifully with tomatoes and with beans (hence the pasta sauce). Like parsley, it is best added close to the end of the cooking.
Note: In postscript to this post, there seems to be a lot of variability in Scots lovage. One plant I have grows as described above, about 300mm in diameter; a second one from the same supplier (Poyntzfield Herbs) grew into a monster about a metre in diameter and eventually had to be removed. The larger one was in a more fertile spot, so I might divide the remaining one and put it in two different places to see whether the difference was genetic or environmental.