Hogweed is probably one of these plants you don't think of as being edible. Usually you know it because people have warned you about the dangers of its phototoxic sap, that can cause serious skin irritation and burning wounds. However, that is mostly true for the giant hogweed (Heracleum mantegazzianum) and less for common hogweed (Heracleum sphondylium), which is perfectly edible when harvested with care.
Common hogweed is still slightly phototoxic, but so are carrot leaves, did you know? Did you ever get warned about carrots?
Hogweed needs to be harvested when it's young, and please, make sure you can identify it poperly, as it belongs to the umbelifer family, and has some toxic lookalikes. If you have a very sensitive skin and want to be on the safe side: wear gloves.
Young hogweed shoots can be cooked and make a great soup. Older stems need to be stripped.
In Slavic countries it was once a staple vegetable; traditionally it was the main ingredient of borscht. And it was lacto-fermented, which is what i did with the leaves i harvested today. I chopped up the leaves and stems, placed them in a canning jar and covered them with a salty brine solution: in 1 liter of water i dissolved 2 tablespoons of sea salt (using more salt slows down the fermentation process). I didn't cap thightly, as the fermentation process will cause air bubbles and they need to be able to escape. I'm leaving the jar at room temperature now; it will probably become alive in a few days.
The seed is also edible; that's something to experiment with later.