Chopped onions & saute in large stock pot with 2 TBLS butter, until tender.
Add sherry & basil, simmer 5 minutes.
Add water & bring to boil, add chicken base.
In saucepan melt butter, slowly add flour to make roux, until all flour is used.
When water is boiling slowly whip roux in small amounts until all roux
is used..Mixture should be thick.
Let simmer about 5 minutes,
Heat milk & gradually whip into thickened soup
Add croutons & Swiss cheese to bowl of soup...heat, eat & enjoy