In a soup pot, mix together all the ingredients except flour, oil, milk and lemon juice. Bring to a boil, and simmer for 15 minutes. In a separate stock pot, lightly warm the oil, add flour, and cook for 1 minute while stirring constantly. Keeping the heat low, whisk in the milk and stir until smooth. Add the mushroom soup to the thickened sauce and simmer for 15 minutes. Just before serving, whisk in the lemon juice. Serve with brown rice*.