Heat the oil in a pan and gently fry the onion for 3-4 minutes, or until softened. Stir in the chilli flakes and the plum tomatoes and cook for a further 3-4 minutes.
Stir in the chopped parsley, then add the cooked pasta to the sauce and stir gently to combine.
To serve, pile the pasta onto a serving plate and garnish with the fresh chervil.
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