put mushrooms, onions and stock in a saucepan. cover and bring to boil and simmer for 30 mins. cool slightly and liquidised.

melt butter over low heat, stir in flour and cook for 2-3 mins. remove from heat slowly stir in milk. return to heat, bring to boil, stirring until thicken

add mushroom puree and simmer for 15mins.

season to taste and add cream