Add the butter to a small saucepan over medium heat. Melt the butter stirring frequently. Continue to cook the butter until brown bits form at the bottom of the pan. It will take about 6-8 minutes. Once the butter is brown remove it from the heat.

Cook the pasta in salted water in a large pot until al dente. While the pasta cooks, heat the olive oil in a large skillet over medium-high heat. Swirl to coat the bottom and then add in the shallot, shaved brussels sprouts, red pepper flakes, salt and pepper. Sauté until the brussels sprouts are tender and caramelized, about 6-8 minutes.

Once the brussels sprouts are tender, squeeze in the juice of a lemon and add in the parmesan cheese and pappardelle. Pour in the brown butter and add in about 1/3 cup of the pasta water (more if needed). Toss everything together with tongs until it’s coated in the sauce. Top with the toasted walnuts and extra parmesan cheese before serving.