Heat the butter or vegetable oil in a large skillet over medium-high heat.
Add the finely chopped onion and cook until softened, about 5 minutes.
Stir in the minced garlic and cook for another 1-2 minutes.
Add the reindeer meat to the skillet and cook until browned on all sides.
Pour in the beef or vegetable broth and soy sauce. Stir to combine.
Reduce the heat to low, cover the skillet, and simmer for about 30 minutes, or until the meat is tender and cooked through.
Stir in the heavy cream and season with ground black pepper, salt, and dried thyme (if using).
Cook uncovered for an additional 10 minutes, or until the sauce has thickened slightly.
Enjoy your meal!