Rough Chervil (Chaerophyllum temulum), fam. Apiaceae.
Occurs in shady, humid parts of the forest. It is difficult to see this plant in summer, since these places become densely covered with stinging nettle and other herbs. However, in early spring it is often easy to recognize the tender Chervil greens, somewhat reminding parsley. But it is not possible to guarantee that this is exactly Rough Chervil, since it also may be Garden Chervil (Anthriscus cerefolium), which is edible.
The latin name "temulum" means "drunken", and it indeed has quite strong toxic properties, targeting the nervous system.