Melt the butter in a saucepan over medium heat. If using, add the chicken, celery, or mushrooms and sauté until the vegetables are soft, or the chicken is warm. Add the rice flour and whisk until the flour just starts to brown.

Add the broth and milk while whisking and bring to a boil.

Boil until thickened.

Use immediately in any recipe calling for canned condensed soup or store in the refrigerator for up to a week.