Prepare your steak, ensuring you use proper food handling hygine, and put it in the freezer to par freeze for a few hours.
Put your shallot into your mixer bowl, chop for 1 sec/speed 9/MC on. Scrape bowl down.
Add parsley, capers and cornichon and chop for 1 sec/speed 9/MC on. Scrape bowl down.
Add mustard, olive oil, salt and pepper and combine for 3 sec/speed 3/MC on. Set aside in a bowl.
Without washing the bowl, add your par frozen steak and chop for about 2-3 seconds/speed 7/MC on. The idea is to have a fine dice, but not mush.
Put your steak in with your reserved seasoning, stir through well. Plate up with aioli and top with the raw egg yolk.