Mise en place - Destem the mushrooms and give them a rough chop. Peel and finely dice the onion. Trim and finely dice the carrot and celery. Grate the garlic using a microplane.
Trim and sweat the mushrooms - Add the mushrooms to a dry pan with a generous amount of salt and cook until the mushrooms release all of their liquid. Continue until most the liquid evaporates. Remove from the pan and set aside.
Saute the veg - Melt the butter in the same pan that you cooked the mushrooms in. Add the onion, carrot, and celery and cook until very, very soft. You want the veg to add flavor but not much texture - the veg should melt into the broth.
Add the mushrooms - Add the garlic, cooked mushrooms (and any residual liquid), and thyme. Cook for 5 minutes on medium low heat.
Simmer - Add the water, wine, stock, Worcestershire sauce, and scant sprinkle of red pepper flakes. Season with salt and pepper. Reduce to low an simmer for 30 minutes to an hour.
Finish and Serve - Stir in half and half. Taste and add more salt and pepper if needed.