Preheat the oven to 200C/Gas Mark 6. Scrub the potatoes well. Pour the salt on to a baking tray and lay the potatoes on top. Bake for 1½ hours or until the skins are crisp and the flesh soft. While the potatoes are still hot, scoop out the flesh into a bowl. Warm the butter and milk in a pan over medium heat.
Start to mash the potatoes and slowly add the milk and butter. Mix until very smooth and glossy, then season to taste. Serve immediately.
Shallot and parsley marmalade method
Heat a heavy-based saucepan and add a drizzle of olive oil. Add the shallots, season with salt and pepper and sweat gently for 4-5 minutes.
Pour in half the white wine and reduce right down until dry, then repeat with the rest of the wine. On a medium heat, add the mustard and chopped parsley to the cooked shallots.
Heat the oven to 200C/Gas Mark 6. Heat a heavy-based ovenproof pan and add a drizzle of oil. Once hot, add the sausages and cook, turning, for a few minutes to colour evenly.
Serve the sausages alongside the mashed potatoes and shallot and parsley marmalade.