Heat a large, non-stick skillet over medium-high heat. Melt the butter in the skillet. Add the beef stew meat. Season with salt and pepper. Cook, stirring occasionally, until the beef is starting to brown. Transfer the cooked beef to a slow cooker set on LOW heat.
Return the skillet to the heat. Add the mushrooms and cook for about 5 minutes, until starting to release their liquid. Add the onions and cook for a few more minutes, until the onions are starting to soften and the mushrooms are starting to brown.
Add the wine and bring to a simmer. Add the chestnuts, squash, apple butter, mustard and fresh herbs. Stir well and add everything to the slow cooker with the beef.
Cover the slow cooker and cook on LOW heat for about 6 hours, or until the beef is very tender. Serve the stew over buttered egg noodles.