Mix flour and spices:
Combine the flour, salt, pepper, and paprika in a shallow dish, stirring to blend.Dredge beef in flour:
Dredge each piece of beef in the flour mixture, ensuring an even coating.Sear beef in batches:
In a large stockpot, warm the butter and olive oil over medium-high heat. Working in batches to avoid overcrowding, sear the beef on all sides until browned. Transfer the browned meat to a plate and set aside.Sauté vegetables:
If the pot seems dry, add a bit more butter or oil. Sauté the garlic, onion, carrots, and celery until they begin to caramelize or soften, about 5 minutes.Add broth and beef:
Pour in the beef broth, then stir in the tomato paste, potatoes, Worcestershire sauce, bay leaf, and rosemary. Return the beef to the pot.Simmer until tender:
Raise the heat to bring the stew to a boil, then reduce to low, cover, and simmer for 60 to 90 minutes, until the beef is fork-tender.Thicken with slurry:
In a small bowl, whisk together the cornstarch and water until smooth. Gradually drizzle the slurry into the stew while stirring constantly. Continue cooking uncovered for 10 to 15 minutes, stirring now and then, until the stew thickens.Remove bay leaf:
Remove and discard the bay leaf.Stir in peas:
During the final 5 to 10 minutes of thickening, stir in the peas to warm them through without turning mushy.