Heat oven to 200˚C. Place potatoes on a baking tray and prick them all over with a fork.Bake for 1 hour or until very tender.Slice potatoes in half lengthwise. Allow excess steam to escape.When potatoes are cool enough to handle with a clean dish cloth, scoop the flesh out of the skins and pass through a potato ricer. If you don’t have one, simply mash them with a potato masher. In a bowl combine the potato, egg yolk ,parmesan, nutmeg and salt. Mix together with a fork. Sprinkle the flour evenly over the potato mixture and very gently fold the mixture together using a spatula.Turn dough onto a lightly floured worksurface. Divide dough into 4. Roll each piece into a 2-3cm thick rope. Cut the rope into 3cm pieces.If you want to add the traditional little lines you can gently roll each piece down a wooden butter pat or the back of a fork. Place finished gnocchi on a lightly floured baking tray. Repeat with the remaining dough.Cook gnocchi in a pan of boiling salted water for 2 to 3 minutes – as soon as they float up to the surface they are cooked. Heat a large frying pan and add about 2 Tbsp(30g) of the butter. Add the mushrooms and cook until golden brown. Season. Now add the rest of the butter and when sizzling add the paprika and sage. Cook until fragrant and nutty. Using a mesh spider or slotted spoon, drain the gnocchi and transfer directly to the pan and toss in the buttery mushrooms. Cook until the gnocchi start getting golden brown crispy bits on each side. Add sun-dried tomatoes and finish with a good squeeze of lemon juice. Season to taste. Serve gnocchi onto plates swished with a little crème fraîche. Finish with a few shavings of parmesan and serve.