Cook the pasta in a large saucepan of unsalted boiling water for 3–4 minutes, or according to packet instructions, until al dente. Drain and return to the pan to keep warm.
Meanwhile, drain the olive oil from the tins of anchovies into a large frying pan and add the garlic. Cook over a moderate heat for 1 minute, then add the anchovies. Cook for 2–3 minutes until the anchovies begin to soften and break up.
Add the parsley and chilli flakes, if using, then stir in the lemon juice. Add the drained pasta to the frying pan, season with pepper and toss to mix. Stir in most of the Parmesan, reserving a little for garnish. Divide the pasta between 4 bowls, sprinkle with the reserved Parmesan and serve immediately with a rocket salad.