Pat the beef chuck cubes thoroughly dry with paper towels. In a large shallow bowl, toss the beef cubes with the flour, salt, black pepper, and garlic powder until evenly coated on all sides.

Heat 1 tablespoon of olive oil in a large heavy skillet or cast iron Dutch oven over medium-high heat. Working in two batches to avoid crowding, sear the beef cubes for 2 to 3 minutes per side until deeply browned with a rich golden crust. Transfer the seared beef into your slow cooker crockpot basin.

Pour 1/2 cup of beef broth into the hot skillet, using a wooden spoon to vigorously scrape up all the delicious browned bits (fond) stuck to the bottom of the pan. Stir in the tomato paste and Worcestershire sauce until completely smooth, then pour this flavorful liquid into the slow cooker.

Add the chopped onions, minced garlic, halved Yukon gold potatoes, thick-cut carrots, celery, dried thyme, crushed rosemary, and bay leaves into the crockpot. Pour in the remaining 2 1/2 cups of beef broth and gently stir everything to combine.

Cover with the slow cooker lid and cook on LOW for 7 to 8 hours (or on HIGH for 4 to 5 hours) until the beef cubes are luxuriously fork-tender and practically fall apart when pressed with a fork.

During the final 15 minutes of cooking, stir in the frozen sweet green peas and let them warm through until vibrant and tender. Discard the bay leaves (and herb stems if using fresh).

Taste the gravy and season with additional salt and freshly cracked black pepper if desired. Ladle into deep warmed bowls, garnish generously with fresh chopped flat-leaf parsley, and serve piping hot alongside thick slices of warm crusty sourdough bread with salted butter!