Preheat a hibachi grill. Preheat an oven to 180C. Preheat a water bath to 55C.
Lay a sheet of aluminium foil onto a clean work surface. Lay a sheet of baking paper on top of the foil.
Place the potatoes into the centre of the baking paper. Season well with sea salt. Add 2 sprigs of rosemary and a good drizzle of extra virgin olive oil.
Wrap the potatoes up in the aluminium foil to make a sealed parcel. Place the parcel onto the coals of the hibachi grill and set aside to cook until soft, about 1 ½ -2 hours.
Meanwhile, for the Walnut Cream, place the sliced shallot and olive oil into a small saucepan over medium heat and sweat off until shallots have softened, stirring occasionally.
Add the walnuts and continue to cook, stirring to coat and warm through. Add the commandaria, being careful as it may flame, and continue to cook until reduced slightly, about 3-4 minutes.
Reduce the heat slightly, then add the cream and continue to stir until the mixture has reduced and liquid has thickened and turned a chocolate brown colour, about 20-25 minutes.
Remove from the heat and pass the liquid through a fine sieve, discarding the walnuts. Transfer the liquid to a piping bag and set aside in the fridge until needed.
For the Potato Cloud, make a bed of salt on a small tray. Place the potato on top of the bed of salt and bake in the oven until cooked through, about 1 hour.
Remove the potato from the oven and allow to cool. Peel the skin from the potato and reserve.
Heat the oil in a small saucepan over medium heat to 180C. Once hot, add the potato skin pieces and fry until golden and crisp, about 30-25 seconds. Remove the skins from the oil and place on paper towel to drain. Reserve the saucepan of oil on the heat.
For the Potato Chips, to the reserved saucepan of oil, add the potato slices and fry until crisp, about 30-45 seconds. Remove from the oil and drain on paper towel. Season well with salt then set aside until needed.
Pass the baked potato flesh through a fine sieve and set aside until needed.
Heat the milk in a medium saucepan over medium heat and bring to a simmer. Add the fried potato skins and shallots, remove from the heat and set aside to infuse for a further 20 minutes. Pass infused liquid through a fine sieve into a clean medium sized bowl.
Gradually add the passed baked potato flesh to the infused milk and whisk until the mixture is smooth and reaches the consistency of pouring cream. Season with salt, then transfer to an iSi gun and charge twice with carbon dioxide.
Sit the iSi gun in the water bath preheated to 55C until needed.
For the Garlic Butter, place the butter and black garlic into a small saucepan over medium heat until the butter has browned but not burnt, about 4-5 minutes.
Remove from the heat and stir in the buttermilk, the mixture will split. Continue to stir well until combined and smooth.
For the Steamed Potato Noodles, peel the potato. Pass the potato through the spiraliser machine to achieve long noodles.
Heat a medium saucepan of salted water over medium heat and bring to the boil. Add the potato noodles and cook until just soft, about 1-2 minutes. Remove from the water and drain well and plunge into an ice bath for 1 minute. Drain well, season with salt and set aside.
To plate, pipe some of the Walnut Cream into the bottom of the bowl. Use a fork to gently crush the Baked Potatoes and place 2 on top of the Walnut Cream. Spoon some Garlic Butter over the crushed Baked Potatoes. Add some Boiled Potato Noodles and a sprinkle of the Fried Potatoes. Remove the iSi gun of Potato Cloud and shake well. Dispense the Potato Cloud over the top to completely cover the entire dish. Top with a teaspoon of caviar.