Melt butter in a skillet over medium high heat. Add mushrooms and cook until tender, about 3 minutes. Add garlic and cook until fragrant, about 30 seconds.
Sprinkle flour over the mixture and stir to create a smooth paste. Slowly add half and half and continue to stir to prevent any lumps. Add soy sauce, salt, and pepper; stir to combine. Taste and adjust seasoning to your liking.
Creamy Mushroom Garlic Sauce · Dinner Match Lab | Dinner Match Lab