Pat beef chunks dry with paper towels, then season generously with salt and black pepper.

(Optional) Heat olive oil in a large skillet over medium-high heat. Sear the beef chunks for 2-3 minutes per side until nicely browned. Work in batches if needed.

Place halved baby potatoes in the bottom of the slow cooker. Add seared beef chunks on top. Scatter onion and carrots in if using.

In a small bowl, melt butter. Stir in minced garlic, Italian herbs, red pepper flakes (if using), and chopped parsley.

Pour beef broth evenly over the beef and potatoes. Drizzle the garlic butter sauce over everything and gently toss to distribute.

Cover and cook on LOW for 7-8 hours or HIGH for 4-5 hours, until beef is fork-tender and potatoes are soft but not mushy.

Taste the sauce and adjust salt and pepper as needed. If the sauce is too thin, let it sit uncovered for 15 minutes or mash a couple of potatoes into the broth for thickness.

Transfer beef and potatoes to a serving platter, spoon extra sauce over, sprinkle with fresh parsley, and serve warm.