Wash the mushrooms, if using Shiitake remove stems, and thinly slice. Set aside.

Heat a large non stick pan on medium heat and add the butter and garlic. Cook the garlic until fragrant, maybe 1 or 2 minutes but do not let the garlic or butter brown.

Now add the mushrooms and cook until nicely browned and any water they released has cooked off.

Reduce heat to low or medium low and add the flour, continue to cooking, stirring often until the flour turns golden brown.

Whisk in the stock and whisk until all the flour has dissolved into the stock, then add the thyme, sage, season with black pepper as desired. Increase the temp to medium, as the gravy starts to simmer, it will thicken. Taste and adjust salt and pepper as desired, the salt will depend on the type of stock or broth you used.

Allow the gravy to simmer for 5 to 7 minutes to reach your desired thickness, and keep in mind, the gravy will also thicken as it cools.

Serve over mashed potatoes.