1. Preheat the oven to 200 degrees. Add the rock salt to an oven tray and place the potatoes on top. Prick the potatoes with a knife before baking for 50-60 minutes until the skin is crispy and the potatoes soft throughout. Remove the potatoes from the oven, cut in half, and scoop out the pulp, discarding the skins. Press the pulp through a ricer and into a large bowl, or mash well with a potato masher if you don’t have a ricer. Stir in the egg yolks, Parmesan and butter and set aside at room temperature for later use as the topping.
2. Heat a large pan and add the vegetable oil. Add the onion and cook for three minutes, then add the garlic, carrot and celery, and cook for five minutes, stirring well. Add the butter and lentils and cook for another three minutes, stirring regularly. Deglaze the pan with the red wine, simmering until the wine has reduced by half.
3. Stir in the tomato paste and soy sauce. Add the vegetable stock, bay leaf, thyme leaves and chopped rosemary. Bring to the boil, then reduce the heat to low. Allow to simmer for 25 minutes, stirring regularly, until the lentils are just cooked. Remove the pan from the heat and season with salt and pepper.
4. Spoon the lentil mix into an ovenproof dish, filling until two-thirds full. Spoon the mash over the top of the mix, spreading evenly with the back of a spoon. Place in the oven and cook for 25-30 minutes at 200 degrees until golden brown all over, then remove from the oven and allow to sit for 10 minutes before garnishing with some more thyme leaves and serving.

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