Pat the venison stew meat dry with paper towels and season evenly with the sea salt and black pepper.
Heat the ghee in a heavy-bottomed pot or Dutch oven over medium-high heat.
Sear the venison in the hot pot until browned on all sides, then remove the meat and set it aside on a plate.
Add the diced onion, sliced carrots, celery, and halved mushrooms to the same pot, sautéing for 5-7 minutes until the onions are translucent and mushrooms have softened.
Stir in the minced garlic and tomato paste, cooking for 1 minute until the mixture is fragrant and the paste darkens slightly.
Pour in the red wine to deglaze the pot, using a wooden spoon to scrape up all the browned bits (fond) from the bottom.
Return the venison and any accumulated juices to the pot, then pour in the beef bone broth.
Add the fresh thyme sprig and bay leaf, bringing the liquid to a gentle boil.
Reduce the heat to low, cover the pot with a tight-fitting lid, and simmer for 90 minutes or until the venison is fork-tender.
Remove the thyme sprig and bay leaf before serving warm in a shallow bowl.