For the gnocchi: Put the whole potatoes into a large pot and cover with water. Bring to a boil and cook until they are tender when pierced with a fork. Let them cool slightly, remove the skins and put them through a food mill or ricer directly onto a floured work surface. Add the Parmesan, fenugreek, garam masala, paprika, salt, pepper and egg and gently begin to knead, adding flour as you go. You may not need all the flour, so add it in increments. Continue to knead until a loose dough forms, taking care not to overwork it as it will become tough. Cut the dough into 3 or 4 big pieces, and then roll each piece into a long rope, about 1/2-inch in diameter. Cut each rope into 1-inch pieces and gently roll along the tines on the back of a fork to create a ribbed appearance. Cover with a cloth until ready to cook.
For the mushrooms: Melt the butter in a large skillet over medium-high heat. When it begins to foam, add the onions and saute until softened, about 3 minutes. Add the garam masala and stir. Add the mushrooms and continue to saute until golden brown, 6 to 8 minutes. Pour in the wine and stir and cook until it has reduced slightly. Pour in the cream, stir well and season with salt. Allow to reduce until the cream has thickened and coats the back of a spoon, 5 to 6 minutes. Stir in the arugula and let it wilt. Keep warm until ready to serve.
To finish the dish: Bring a large pot of water to a boil and add some of the gnocchi. Avoid crowding by cooking them in batches. When they float to the surface, remove then with a slotted spoon and drain. Spoon the gnocchi into shallow bowls and ladle some sauce over them. Garnish with shavings of Parmesan and pepper.