Scrub the potatoes and parsnips well and turn them with a little butter, salt and pepper and thyme and place into an oven proof dish. Cook in oven at 170 degrees for 30-40 minutes until tender. Once done, mix with coarsely chopped parsley.
Char steak on a smoking hot pan for 3-4 minutes on each side to get a good color. Place the pan in the oven at 200 degrees for 20 minutes and turn occasionally in order for the cut to be cooked equally. Remove the steak out and let it rest for 5-7 minutes and it is ready for serving
Bring the soft butter into a bowl and whip it white and airy, seasoning garlic, herbs, lemon juice, salt and pepper