Season the beef cubes with salt and black pepper, ensuring they are evenly coated.
In a large skillet, heat the olive oil over medium-high heat. Add the seasoned beef cubes and sear them for about 2-3 minutes on each side until browned.
Transfer the seared beef to a slow cooker.
In the same skillet, reduce the heat to medium and add the butter. Once melted, add the minced garlic and sauté for about 1 minute until fragrant.
Pour the garlic butter mixture over the beef in the slow cooker.
Cover and cook on low for 4-5 hours or on high for 2-3 hours, until the beef is tender.
Once cooked, stir the beef gently to coat it in the garlic butter sauce.
Serve warm, garnished with chopped parsley if desired.