In a large skillet or saucepot, melt the butter over medium heat. Add the chopped mushrooms and sauté until soft and browned—about 5 to 7 minutes. Stir occasionally to keep them from sticking.
Heat the Broth and Seasonings
Once the mushrooms are softened, pour in the vegetable broth, ½ cup of the milk, garlic powder, salt, pepper, parsley, and paprika. Bring the mixture to a light boil and let it simmer for about 90 seconds so the flavors can come together.
Make the Thickening Mixture
In a separate bowl, whisk together the flour and remaining 1 cup of milk until completely smooth.
Thicken the Soup
Slowly pour the flour mixture into your hot broth while whisking constantly to prevent lumps. Bring it back to a boil and continue whisking until it thickens. This doesn’t take long—don’t walk away!
Cool Slightly and Use as Needed
Remove the soup from the heat and let it cool for a few minutes. It’s now ready to use in any recipe that calls for canned cream of mushroom soup—or just enjoy a warm bowl with some crusty bread.