Generously season the cubed beef with salt and pepper.
Heat the oil in a dutch oven over medium-high heat and brown the beef on all sides, about 5 minutes. Remove the beef and any remaining liquid to a bowl and set aside.
Melt the butter in the now empty dutch oven and add the onion, celery and carrots. Cook, stirring occasionally, until the vegetables are soft, about 6 minutes.
Stir in the the sliced mushrooms and garlic and cook for 3 more minutes.
Pour in the broths and scrape the bottom of the pot to release any stuck on bits. Add the wild rice and bring to a boil.
Return the beef and any liquid back into the pot and reduce the heat to medium-low. Cover and simmer for 1 hour or until rice is tender. Add salt and pepper to taste.
