100 ml (3 1/2 fl oz) dry white wine or vegetable stock
250 ml (8 fl oz) single cream
salt and pepper
4 teaspoons grated Parmesan-style cheese, to serve
Heat the butter and oil in a large nonstick frying pan until the butter is frothing. Add the leek and garlic, and cook for 2–3 minutes, until beginning to soften. Add the mushrooms and tarragon, and cook for a further 4–5 minutes, until soft and golden.
Meanwhile, cook the pasta in a large saucepan of lightly salted boiling water for 11 minutes, or according to packet instructions, until al dente.
Pour the white wine and cream into the mushrooms, and season generously with salt and pepper. Simmer gently for 6–7 minutes.
Drain the pasta and stir into the sauce. Spoon into 4 shallow bowls and serve immediately, sprinkled with grated Parmesan.