Bring a large pot of salted water to a rapid boil over high heat. Add pasta and cook until al dente. Reserve ½ cup of pasta water, then drain pasta.

Meanwhile, warm ¼ cup of olive oil in a large skillet over medium heat. Add garlic and sauté until lightly toasted and fragrant, about 2 minutes. Add greens, a handful at a time, and cook until greens are wilted and liquid has cooked off. Season with salt and pepper.

Toss toasted hazelnuts with oregano and red pepper flakes in a small bowl. Drizzle with remaining ¼ cup of olive oil and season with salt and pepper. In a separate bowl, combine mascarpone, lemon zest, lemon juice, heavy cream, and parmesan.

Return drained pasta and ¼ cup of reserved pasta water to pasta pot. Add cooked greens and warm over low heat. Add mascarpone mixture and toss, adding more pasta water as needed, until sauce coats pasta. Add half the hazelnut mixture and stir gently to combine. Divide pasta evenly among bowls and garnish with remaining hazelnut mixture.