Melt the butter in a saucepan, add vegetables, and fry gently for 5 minutes until soft but not browned.
Stir in the flour and cook for 1 minute. Remove from heat.
Stir in the wine and stock and return to heat. Bring to the boil, stirring continuously until the soup thickens then simmer over low heat for 30 minutes.
Cool slightly and liquidize or press the soup through a sieve. Return to the rinsed out pan. Add the milk and heat gently. Stir in the Stilton and English Cheddar, seasonings and heavy cream until melted.
** Do not let the soup boil at this stage or it will curdle. Serve garnished with croutons.