Melt 2 tablespoons butter in a large nonstick skillet over medium heat.
Add the onion and cook for 5 minutes until softened.
Add the mushrooms and garlic and cook for about 4 more minutes.
Add the remaining butter. When melted, add in the flour and stir in until the onion and mushrooms are well coated.
Add the milk gradually, stirring in well.
Then mix in the bouillon, thyme, and soy sauce. Bring to gentle simmer and cook for about 3 minutes until thickened. Add salt to taste.
If you want chunky gravy, then you’re done. If you’d prefer creamy gravy, then pour the gravy mixture into a blender or into a container to use with your immersion blender (if using a regular blender, make sure to allow the gravy to cool before blending for safety). Blend for a minute or so until the desired consistency. Then serve.