I was inspired to cure the fillet by Fergus Henderson's cookbook "Nose To Tail Eating." I added the rocket/arugula because I love it, and the pale celeriac and dark meat seemed to need a shot of green. I substituted horseradish for the Dijon mustard, and sour cream for the creme fraiche, in his dressing. —KristenF
Place the rosemary sprigs in the bottom of a plastic container that will easily hold your beef, and has a tight-fitting lid.
Generously cover the bottom of the container with half the salt-sugar mixture, then place 4 rosemary sprigs on the mixture, place the beef fillet on top of them, and place the remaining rosemary sprigs on top of the fillet.
Pour the remaining salt-sugar mixture over the beef fillet and cover the container tightly.
Wait three days, then uncover the container and wipe the salt-sugar residue off with paper towels.
Celeriac Salad and Creamy Horseradish Dressing
Slice the celeriac very thin, like matchsticks, drizzling lemon juice over as you go to prevent darkening.
Mix remaining lemon juice with sour cream, sea salt and pepper.
Slice the beef very thin, across the grain.
Arrange the celeriac and beef in a pleasing way on a platter, then scatter with rocket.