Pat the beef cubes dry and season generously with salt and pepper.
In a large skillet, melt 2 tbsp of butter over medium-high heat. Sear the beef cubes in batches until browned on all sides. Transfer the seared beef to your slow cooker.
Add the remaining 2 tbsp of butter to the skillet and melt. Add the chopped onion and cook until softened, about 5 minutes. Add the minced garlic and cook for another minute until fragrant.
Add the onion and garlic mixture to the slow cooker with the beef.
Add the quartered potatoes to the slow cooker.
Pour in the beef broth. Sprinkle the thyme and rosemary over the ingredients.
Cover and cook on low for 6-8 hours or on high for 4-5 hours, until the beef is tender and the potatoes are cooked through.
Before serving, gently stir to combine the sauce and ingredients. Taste and adjust seasoning with salt and pepper if needed.
Garnish with fresh chopped parsley.