- For the gnocchi: In a large pot of boiling water over medium heat, simmer potatoes until fork tender. Pass potatoes through a food mill. On a table, form flour into a mound and fold in cooked potatoes, grated nutmeg, parmesan cheese, salt, and pepper. Form a hole in the center of the mound and slowly pour in egg yolks. Gently knead dough to keep it light and fluffy. With a bench scraper, cut small pieces of dough to desired size (about 1 inch) and roll with your hand. Cook in batches in boiling, salted water over medium-high heat for 3 to 5 minutes, or until pasta is slightly firm and floats to the top.
- For the mushrooms and sauce: In a hot sauté pan, drizzle in olive oil, then add cold butter. Cook until butter turns brown and begins to give off a nutty aroma, then add oyster and maitake mushrooms, cooking until golden brown. Heat gnocchi in pan with mushrooms for approximately 2 minutes; season with salt.
- To assemble: In small bowls, divide gnocchi and place in center of the bowl. Pour brown butter sauce with the mushrooms over gnocchi. Finish with parmesan and garnish with parsley.