1 lb. broccoli
1 lb. pasta
2 tbsp. unsalted butter
2 tbsp. olive oil
1 small onion, finely chopped
3-4 cloves garlic, minced or pressed
½ tsp. red pepper flakes
1 tsp. salt
Up to ½ cup heavy cream (or greek yogurt)
Freshly ground black pepper, to taste
Grated Parmesan, for serving
Bring a large pot of water to boil. Meanwhile, chop the broccoli crowns into florets. Use a vegetable peeler to remove the tough outer skins of the broccoli stems, and chop the stems into ½-inch discs. When the water is boiling, add the broccoli to the water to boil briefly just until fork-tender, about 3-4 minutes. (Alternatively, add a steamer basket above the water and steam the broccoli until fork-tender.) Remove to a bowl, leaving the water in the pot. (Use a skimmer or strainer to remove the broccoli if you boiled it.)
Maintain the water at a boil. Add the pasta to the pot and cook according to the package directions until al dente. Reserve 1½ cups of the pasta water and then drain the pasta well. Set aside.
Return the pot to the heat. Add the butter and olive oil to the pot over medium-high heat, heating until the butter is melted. Add the onion to the pot and cook, stirring occasionally, until the onion is tender, about 5 minutes. Stir in the garlic, red pepper flakes and salt and cook 1-2 minutes more. Return the cooked broccoli to the pan and cook 1-2 minutes more to heat through. Season with pepper to taste.
Transfer the broccoli mixture to a food processor or blender. Pulse in short bursts, scraping down the sides as needed, until the mixture is finely chopped. Add in the cream or greek yogurt and process until smooth. If needed, add the reserved pasta water a little bit at a time just until the sauce is smooth and creamy. (Don’t overdo it – you don’t want a watery sauce!) Season with freshly ground pepper to taste. In a large bowl (or in the pot), toss the pasta with the sauce. Serve with freshly grated Parmesan.