For years I thought this was an astrantia because I remember the tag calling it a masterwort. Unfortunately this is a case where a common name is used for more than one genus of plants.
This is Peucedanum ostruthium ‘Daphnis’.
Its in the carrot/parsley family (obviously, just take one look at those umbel flowers!)
Its a zone 5-9 shade plant. For years it was a small delicate beauty (probably because i’m on the edge of its zone). Then with this years mild winter it exploded in size !
I’m guessing in warmer climates it might behave more aggressively but for whatever reason its perfect for my garden.