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Meanwhile, make the sauce. Melt the margarine in a large heavy saucepan. Gently cook the leeks in and garlic until tender. Drain the ceps, chop very finely and add to the pan.
Stir in the flour. Take the pan off the heat and gradually add the stock and white wine, stirring all the time to prevent lumps from forming.
Put the pan back on the heat, bring to the boil, then simmer for 5 minutes until the sauce has thickened, stirring all the time.
Stir in the tarragon and seasoning to taste, then add the soya cream.
Toss the cooked pasta into the sauce and serve immediately with garlic bread a mixed green salad.
posted by Mr Falafel