Mushroom and Tarragon Soup

450g (1 lb.) Mushrooms
2 medium Onions
1 Bunch Fresh Tarragon (or 1 Teaspoon Dried)
60g (2 oz.) Butter
60g (2 oz.) Flour
1 tablespoon Lemon juice
1 pt. Milk
1 pt. Chicken Stock

Peel and chop the Onions. Melt the butter over a gentle heat and cook the chopped onion at this heat until soft (this will take 10 mts. or so).
Chop the tarragon and add to the pot. Put out your largest chopping board and chop the mushrooms roughly with a large chopping knife until they are in rough dice (their roughness adds to the texture of the soup).
Add these to the pan, increase the heat and cook briskly until the mushrooms are soft and most of their liquid has evaporated.
Meantime bring the milk and stock to the boil together.
Add the flour to the mushrooms and stir in well.Add the boiling stock and milk to the soup and bring it back to the boil stirring all the time.
Taste and season with salt and black pepper and the lemon juice.
Let it simmer for 10 mts. and serve.