Heat some olive oil in a heavy skillet. Gently fry the garlic, fennel, fennel seeds and chilli for 4 minutes. Add the vinegar and half of the dill. Season with pepper and salt. Cook the pasta al dente and drain. Add the pasta to the sauce and mix well. Add more olive oil if needed. Spoon the pasta in deep plates. Top with the crushed pistachio. Finish with the remaining dill.