The Preparation
Melt butter in a large pot over medium heat.
Add sliced mushrooms and cook until browned.
Add diced onion and cook until softened.
Add garlic and fresh thyme, cook 1-2 minutes.
Sprinkle flour over mushrooms for a roux, stir 1-2 minutes.
Add Dijon mustard and stir.
Pour in broth, bring to a simmer.
Cook 15-20 minutes.
Use immersion blender to desired consistency.
Stir in heavy cream, season with salt and pepper.
Heat through and serve.