Cut the mushrooms into slices.
Melt the butter in large frying pan.
Add in the mushrooms, garlic and onions. Cook until the onions become soft.
Blend in 2 tablespoons flour and stir.
Add in the chicken broth and heat until slightly thickened, while stirring frequently.
Stir the cream with the additional 1 teaspoon flour and seasonings.
Add the cream to the soup, heat to thicken while stirring frequently.Serve hot.