To prepare the lamb, using a knife take most of the skin off and discard and remove any silver skin, slice into circles 1 cm (½ in) thick and leave at room temperature.
In a saucepan over a medium–low heat, combine the onion, garlic and 40 ml (1¼ fl oz) of the oil. Sweat it, but don’t get any colour on it. Once it’s translucent, add in all the spices and set to the side to cool. Once it has cooled, fold through the herbs.
Preheat the oven to 200°C (400°F). To salt-bake the celeriac, layer the salt on a baking tray and then cover with a sheet of baking paper. Put a few really thin slashes through the paper so the salt can slightly seep through. Top with the celeriac then cover the tray with foil and roast in the oven for 50 minutes.
To make the tarator, in a blender blitz everything but the parsley together with 2 tablespoons of water until it is starting to get smooth but is still textured, then fold through the parsley and set aside.
When the celeriac is roasted, in a large non-stick frying pan over a medium–high heat, melt the butter and remaining oil and add the celeriac. Using a lid that is smaller than the pan, press the celeriac down and sear it until it colours on one side, then turn the heat off and let it continue to cook in the pan.
To prepare the lamb, get a hot griddle or large frying pan very hot and, in batches so you don’t overload the griddle, quickly sear the lamb slices on one side. Remove from the pan, then dice. Season this with the onion, herb and spice mix. They should take 30 seconds to sear.
To serve, spoon the tarator on the plates. Loosely place the tartare over the plate in an almost round mound. Roughly chop the celeriac, then arrange it, shining the golden side up, on one side of the plate. Dust with paprika and enjoy!