Add the butter to a large, non-stick skillet set over medium heat. Allow it to melt and then brown. It will get quiet and smell nutty when it’s ready. Pour the browned butter into a food processor, and don’t wipe out the skillet.

Add just enough olive oil to the pan to coat the bottom (usually a around 3 TBSP). Fry the sage leaves, in batches as needed, just until lightly browned and crisp. Transfer to the food processor with the browned butter. 

Add the hazelnuts to the sagey oil and toast until golden brown and fragrant; about 1 to 2 minutes (this goes fast). Reserve about 2 TBSP of these to use as a topping later, and transfer the rest to the food processor, along with the flavored olive oil from the pan. Don’t wipe out the pan.

Add the arugula and garlic to the food processor and process the pesto mixture into a paste. With the motor running, drizzle in enough olive oil to reach your desired pesto consistency – I usually do about ⅓ cup. Taste and adjust seasoning as needed (salt, pepper, more arugula, etc.). 

With the heat still set to medium, add the mushrooms in a single layer to the same skillet and let them brown and crisp up – the trick is not to touch them while they cook. The less you mess with them, the browner, and crispier they’ll get. Cook until they’re browned and crispy all over – 8 to 10 minutes. (NOTE: the non-stick pan makes it so we don’t need any extra oil to cook the mushrooms).

Meanwhile, prepare the raviolis according to package directions, in well salted water (like the sea). Drain and return to the skillet. Add about ¼ cup of the pest to the pan and gently toss with the ravioli, helping each one to get a thin coating. Add the mushrooms to the pan. 

To serve, pile the ravioli and mushrooms onto serving plates (or a big platter) and top with extra spoonfuls of pesto, along with some reserved toasted hazelnuts and a scattering of fresh arugula. Enjoy!