Heat the butter in a large saucepan. Add minced shallots and cook until translucent.
Add mushrooms and cook until all the liquid is released and mushrooms are starting to brown.
Sprinkle flour on top of mushrooms and stir while cooking until all white streaks are gone, about 30-60 seconds.
Slowly pour in broth 1/2 cup at a time, mixing after each addition to get the mixture smooth.
Cook on medium low heat until slightly thickened, about 10-15 minutes.
Mix in dried thyme and salt to taste, as well as splash of cream if you wish.