Clean mushrooms and slice
Melt butter/margarine in a pan without browning
Add lemon juice and whitewine and steam mushrooms for 5 minutes.
Remove mushrooms from pan.
Add flour to pan and whisk until paste-like
Add stock and cream gradually while whisking until desired consistence achieved.
Add 1/2 vegetable stock cube.
Season to taste with salt and pepper.
Return mushrooms to pan and re-heat before serving