1) Place the whole unpeeled potatoes into a medium saucepan with cold water on medium heat. Bring the potatoes to a boil and cook for 20 to 25 minutes until soft enough to mash. Check with a knife to see if the potatoes are cooked through and tender. Once ready drain the potatoes.
2) When cool enough to handle, peel each potato, cut them into small pieces and pass them through a potato ricer over a medium-sized bowl. Add the flour, Parmesan, egg yolks, nutmeg, thyme, salt and pepper and mix into a doughy consistency, adding more flour as needed. Transfer the dough to a well-floured surface.
3) Using your hands, roll pieces of the dough into a rope about 1 1/2-cm in diameter. With a knife, cut the rope into 1 1/2-cm to 2-cm-long pieces. Flour the pieces as you cut them, placing them on a baking sheet that's either floured or lined with waxed paper. Once rolled, you can place the gnocchi in the refrigerator covered with cling film until ready to cook.
4) When ready to cook, place the gnocchi in boiling salted water for about 1 to 2 minutes. They will rise to the top when done. Using a slotted spoon, remove the gnocchi from the saucepan.
In a skillet, add the butter and mushrooms and saute until nicely browned, about 5 to 7 minutes. Add the white wine and reduce by half, about 5 minutes. Add the cream and gently simmer for another 2 to 5 minutes. Once the sauce has simmered, add the gnocchi and cook for 2 minutes.
Garnish with fresh parsley and grated Parmesan.