Homemade mushroom gravy - In a deep pan over medium heat add butter and allow to melt, then whisk in flour to create a thick roux.
Slowly whisk in chicken broth and 1/2 cup of cream until you get a creamy thick mixture. Add more to thin out to your liking. Sprinkle in your salt, onion powder and pepper. Continue to whisk over medium heat until smooth and thick. (if you want thicker, whisk in 1 more tbsp flour)
Stir in mushrooms and reduce heat to low, heating until mushrooms are hot. Taste, adjust seasonings and serve.
Mushroom gravy with cream of mushroom soup - In a skillet or saucepan, melt the butter over medium heat. Add the sliced mushrooms and 2 tbsp. minced garlic, and saute until the mushrooms are golden brown and tender, about 5 minutes.
Add the can of condensed cream of mushroom soup to the skillet. Stir in just enough of the chicken or vegetable broth until it is the right consistency for you. Bring the mixture to a simmer. Stir in just enough heavy cream or milk to add extra creaminess to the gravy. Adjust the thickness. Let the gravy simmer for a few minutes, season to your liking and serve.