Dice the onions and cut the mushrooms into equal slices.
Melt the butter in a pot over medium heat. Add in the diced onions and cook until they are translucent.
Add the mushrooms and sauté until they are tender and lightly golden.
Add the flour and cook for about 2 minutes, stirring constantly. Pour in the broth and stir well to dissolve any lumps of flour.
Season with thyme, salt, and pepper. Let the soup simmer for about 10 minutes, stirring occasionally.
Stir in the half-and-half. Let it come back up to a simmer, then remove from the heat. Enjoy!
