pound bucatini or thick spaghetti
tablespoons unsalted butter
pound spring onions, thinly sliced, including any nice greens (about 4 cups, see Tip)
cups heavy cream
large sprig fresh rosemary
Large pinch of red-pepper flakes
Freshly ground black pepper
cup grated Pecorino Romano
teaspoon finely grated lemon zest
cup chives, finely chopped, more for serving
cup torn mint leaves, for serving
Chopped pistachio, for serving (or use pine nuts or almonds)
- Bring a large pot of heavily salted water to a boil over high heat. Add pasta and cook until it is just shy of al dente, usually 2 minutes less than the package instructions. Reserve about 1 cup pasta water for the sauce (a coffee mug is good for this), then drain the pasta.
- Meanwhile, in a large skillet, melt butter over medium-high heat. Add onions and cook, stirring occasionally, until golden brown at the edges and thoroughly soft, 12 to 15 minutes.
- Add heavy cream, rosemary, 1/2 teaspoon salt, red-pepper flakes, and a few grinds black pepper to the pan, and bring to a simmer. Let cream reduce and thicken, 2 to 4 minutes.
- Reduce heat to low and stir in Pecorino Romano until combined. Add the drained pasta and about 1/2 cup of the reserved pasta water. Toss well to coat the pasta. If the sauce is too thick, add pasta water by the tablespoon; if it’s too thin, let it bubble and reduce for a minute or so. Remove from heat and stir in lemon zest and chives. Taste and add more salt, if needed.
- Serve in bowls, each topped with more chives, mint, a generous amount of black pepper and a sprinkle of pistachios.