For the Roasted Beetroot, lay a sheet of aluminium foil on the bench, drizzle with the oil and sprinkle with the rock salt and ground fennel. Place beetroots on foil, wrap up tightly and place in a small, flame-proof roasting pan. Place in the oven and roast for 45-50 minutes, or until tender.
Remove beetroots from pan and reserve the roasting pan with any pan juices. Peel beetroots then slice into wedges. Season with seas salt to taste and set aside until needed.
For the Sauce, place a large braising pan on the stove top over high heat. Add the bones and drizzle over the oil. Cook, stirring, until bones are caramelised, about 10 minutes.
Add vegetables, 300ml water, mustard seeds and ground mustard. Reduce heat and simmer for 30 minutes.
Meanwhile, place the reserved beetroot roasting pan onto the stove top over high heat. Once hot, deglaze pan with the vinegar and ¼ cup water. Reduce heat and simmer for 3 minutes, scraping the pan.
Pour the contents of the beetroot roasting pan into the simmering beef bones pan. Allow to simmer for a further 10 minutes. Strain through a fine sieve and place stock in a clean saucepan over a medium heat.
Whisk the butter into the stock, one cube at a time, until butter is melted and sauce has emulsified. Season sauce to taste with salt and set aside, keeping warm until needed.
For the Mustard Pickle Radish, place all ingredients, except radish, in a small saucepan over medium heat. Bring to the boil, stirring to dissolve the sugar. Remove the pickling liquid from the heat and set aside to cool to room temperature.
Once pickling liquid is cool, add the radish slices and set aside to pickle for about 10 minutes.
For the Charred Beet Leaves, line a baking tray with baking paper. Place the oil, spices and salt in a small bowl and mix to combine. Rub the beetroot leaves with the oil and spice mix to coat evenly.
Lay the coated beetroot leaves flat on the baking tray, top with another sheet of baking paper and another tray to keep the leaves flat. Bake in the pre-heated oven until crisp and charred, about 8 - 10 minutes. Remove from oven and set 3 leaves aside for garnish. Reserve the rest of the leaves for the Charred Leaf Butter.
For the Charred Leaf Butter, place butter in small frypan and cook over medium heat until butter is a deep brown colour. Transfer to the bowl of a small food processor. Add the reserved Charred Beet Leaves to the food processor and process until butter and leaves are well combined. Set aside until needed
For the Beef, season the eye fillet with fennel and salt to taste and rub with 1 tablespoon of the olive oil. Wrap the fillet in cling film and roll on the bench to form a neat cylinder. Secure both ends of the cling film and place in the fridge to firm.
Once firm, heat remaining oil in a large, oven-proof frypan over high heat. Remove beef from fridge, unwrap and place into the hot pan. Cook beef, turning, regularly until browned on all sides, about 4 – 5 minutes. Transfer the pan to the oven and roast for 10 – 15 minutes, basting regularly with pan juices, until medium rare or cooked to your liking. Remove beef from pan and rest for 5 minutes before serving.
To serve, place 3 spoonfuls of the Charred Leaf Butter around the plate. Slice the rested beef fillet into 12 equal slices and place 3 slices on each plate, resting on the butter.
Add several wedges of Roasted Beetroot to each plate, arranged around the pieces of beef. Lean one Charred Beet Leaf on each piece of beef. Garnish with fresh celeriac leaves and a sprinkle of ground fennel.