Toss beef with flour, salt, and black pepper until the cubes look evenly coated. Brown the beef in hot olive oil until browned on the outside, then transfer to the slow cooker.

Add the onion, garlic, tomato paste, beef broth, Worcestershire sauce, carrots, celery, potatoes, and dried thyme to the slow cooker. Stir to combine so the vegetables are submerged in the broth.

Cover and cook on LOW for 8 hours, until the beef is tender and the stew looks thick and bubbling around the edges. Visual cue: beef should break apart easily with a fork.

Turn the slow cooker to HIGH, then stir the Bisquick baking mix, milk, and chopped parsley into a soft dough. Visual cue: the mixture should hold together as a scoopable, thick batter.

Drop tablespoons of dough over the hot stew in an even layer, leaving space between dumplings. Cover and cook on HIGH for 30-35 minutes without lifting the lid until dumplings are cooked through, visibly puffed and no longer wet in the center.