1/2 cup margarine
1 cup chopped celery
1 teaspoon lemon juice
1 cup sifted all-purpose flour
3/4 cup milk
1/4 cup lemon juice
1/8 teaspoon salt
Melt margarine, celery and lemon juice in the bottom of a large saucepan. Bring to a boil, stirring occasionally. Reduce heat, and simmer for five minutes. Remove from heat, stir in flour, and add milk. Stir gently, without stirring much. Reduce heat to medium, and stir in flour mixture. Return to a boil, stirring frequently. Boil for 10 minutes. Remove from heat, and stir in lemon juice and salt. Pour mixture into slow cooker. Add meat stock, chicken stock, broth, cornstarch, butter, salt, pepper and oil. Bring to a boil; reduce heat, stir, and simmer for one hour.