Pat the cubed beef chuck thoroughly dry with paper towels. Season generously with salt and black pepper, then toss in a shallow bowl with 3 tablespoons flour to lightly coat all sides.

Heat 1.5 tablespoons olive oil in a large heavy skillet or Dutch oven over medium-high heat. Sear beef cubes in two uncrowded batches for 3 to 4 minutes per side until a deep, caramelized brown crust forms. Transfer browned beef into the slow cooker.

In the same skillet, add remaining oil and sauté chopped onions for 2 minutes. Stir in tomato paste, minced garlic, and Dijon mustard for 1 minute until fragrant. Pour in 1 cup of beef broth to deglaze the skillet, scraping up all browned fond from the bottom. Pour pan juices into the slow cooker.

Add the halved potatoes, sliced carrots, celery, remaining beef broth, Worcestershire sauce, thyme, rosemary, smoked paprika, and bay leaves into the slow cooker. Stir gently to combine.

Cover with the lid and cook on LOW for 7 to 8 hours (or on HIGH for 4 to 5 hours) until the beef chuck is so tender it falls apart with a fork and vegetables are meltingly soft.

Remove and discard bay leaves and herb sprigs. For a thicker glossy restaurant-style gravy, whisk cornstarch and water together until smooth, stir into the bubbling stew, and cook on HIGH uncovered for 12 to 15 minutes.

Stir in the frozen green peas and let sit for 3 minutes until tender and bright emerald green. Taste and adjust salt and black pepper as desired.

Ladle steaming stew into deep rustic ceramic bowls. Scatter fresh chopped parsley over top and serve immediately with thick slices of warm crusty sourdough bread or warm buttered dinner rolls!