Cut the broccoli into florets and steam until very soft. Put into a heavy-bottomed saucepan, add the butter and olive oil and mash until all the butter is melted and it is a chunky sauce-like mixture. If you are using anchovies, finely dice them and stir into the broccoli mixture with the lemon zest and chilli flakes. Season with salt and pepper. Cook the pasta in a pot of salty water and then drain, but save ½ a cup of cooking water. Add the pasta and cooking water to the pot with the broccoli mixture and stir through. Serve with Parmesan.