In a medium-sized saucepan over medium-low heat, melt the butter.
Add the mushrooms and stir until coated in the butter. Continue to cook until the mushrooms cook down, release their moisture, and then most of the moisture cooks out, about 10-15 minutes, stirring occasionally.
Add the garlic powder, pepper, onion powder, and salt then stir.
Add the flour. Stir to combine until the mushrooms are coated; the mixture will be thick. Cook the flour mixture for 1 minute, stirring occasionally.
Slowly stream in the chicken broth while constantly stirring to avoid lumps.
Slowly stream in the milk while again stirring constantly.
Bring the mixture to a low simmer while stirring often. Allow to simmer for 2-3 minutes until thickened. Take off the heat until ready to use. Note: the mixture thickens as it cools.
Notes
Please refer to my FAQ’s (Frequently Asked Questions) and ingredient list above for other substitutions or for the answers to the most common questions.
I am assuming half a cup per serving. You will need to use your own trusted nutritional calculator for exact numbers for what you will use this for. Please see my nutritional disclaimer on this recipe card.