Pat beef cubes dry with paper towels. In a large bowl, toss the beef with salt, pepper, and flour until evenly coated. Ensure each piece is lightly floured.

Heat olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat. Working in batches if necessary, brown the beef cubes on all sides, about 2-3 minutes per batch, to develop a nice crust. Do not overcrowd the pot; this ensures proper searing rather than steaming. Remove seared beef to a plate and set aside.

Reduce heat to medium. Add the chopped onion to the pot and cook until softened and translucent, about 5-7 minutes, scraping up any browned bits (fond) from the bottom of the pot with a wooden spoon. This adds significant flavor to the gravy. Add minced garlic and cook for another minute until fragrant.

Pour in beef broth and Worcestershire sauce, stirring well to combine and further scrape up any remaining fond. Add dried thyme and bay leaf. Bring the mixture to a gentle simmer.

Return the seared beef tips to the pot. Ensure the beef is mostly submerged in the liquid. If not, add a little more beef broth or water until just covered. Bring back to a gentle simmer, then reduce heat to low, cover tightly, and cook for 1.5 to 2 hours, or until the beef is fork-tender. Stir occasionally to prevent sticking.

Once beef is tender, remove and discard the bay leaf. In a small bowl, whisk together cornstarch and cold water until smooth to create a slurry. Slowly whisk the slurry into the simmering gravy in the pot. Stir constantly to avoid lumps.

Increase heat to medium-low and continue to simmer, stirring gently, until the gravy thickens to your desired consistency (usually 5-10 minutes). Taste and adjust seasonings (salt and pepper) if needed. The gravy should be rich and flavorful.

Remove from heat. Garnish with fresh chopped parsley, if desired. Serve the hearty beef tips and gravy hot over creamy mashed potatoes, fluffy rice, or wide egg noodles for a complete, comforting meal.