Melt butter in saucepan, add vegetables, and saute for 5 minutes. Stir in flour and cook for 1 minute. Remove from heat, then stir in wine and stock. Return to heat, bring to boil, and simmer for 30 minutes. Add milk and cheeses, stirring constantly. Season with salt and pepper. Mix in cream. Rub through sieve or puree in blender, and reheat without boiling. Serve with croutons.