How to Make It
Cook the whole-wheat pasta in boiling salted water, according to package directions. Reserve 1/2 cup of the cooking water.
Preheat the oven to 350°. Place the hazelnuts on a baking sheet and toast in the oven for 10 minutes, or until lightly browned and fragrant. Remove from the oven and when cool enough to handle, roughly chop them.
In a large frying pan, heat the butter over medium high heat until it is dark brown but not black.
Add all of the mushrooms to the pan. Cook, stirring occasionally, for 7 to 8 minutes, or until the mushrooms are soft and brown. Add the garlic and chile flakes and cook 1 minute more. Add the penne and toss to coat. Sprinkle with a little of the reserved pasta water to create a light sauce. Remove from the heat and stir in the olive oil and Parmigiano-Reggiano cheese. Season with salt and pepper.
Top with the hazelnuts and a little parsley. Serve with the extra cheese.