I would par boil them as if you were going to roast them, then dunk them in cold water, pat dry in a tea cloth and then freeze in containers rather than bags
I leave them in the ground too and dug up one or two a week until Feb/March. They taste sweeter after a good frost too. Just mind your back when the ground is frozen (!) but leave them be, they'll be happy in the ground untilyou need them.
However if you have to dig them up for some reason, then do as Tony advises and par boil them. Ie put them in a saucepan of cold water, bring it to the boil, simmer for 4 minutes and remove. Pop them in a bowl of cold water and then pat dry. Leave to cool and package up for the freezer.
I prep a lot of parsnips at work during Harvest. I admit to never blanching them as they don't need as much cooking like other root veg. They come out fine when used in stews/casseroles.
I agree about not needing as much cooking. I once made the mistake of putting them in the same pan as potatoes. The spuds came out perfectly but the parsnips were mush.