50 g (2 oz) Parmesan cheese, grated, plus extra to serve
salt and pepper
Heat the oil in a large frying pan. Add the spring onions and asparagus and cook for 2–3 minutes until just cooked through. Stir in the tarragon.
Cook the linguine in a large saucepan of lightly salted boiling water according to the pack instructions. Drain, reserving a little cooking water, and return to the pan. Add the cooked asparagus and onion, then add the egg, crème fraîche and Parmesan, season and stir together until creamy, adding a little of the pasta cooking water if needed. Spoon into bowls and scatter over more Parmesan to serve.