Pat the beef cubes dry with paper towels and season with salt and pepper.
Heat vegetable oil in a large Dutch oven or heavy-bottomed pot over medium-high heat.
Sear the beef in batches until browned on all sides, approximately 3-4 minutes per batch, then remove beef and set aside.
Add the diced onion to the pot and sauté for 5 minutes until translucent. Add minced garlic and cook for an additional 60 seconds.
Pour in 1/2 cup of beef broth to deglaze the pot, scraping the bottom with a wooden spoon to release the browned bits (fond).
Return the beef to the pot and add the remaining beef broth, Worcestershire sauce, soy sauce, and thyme.
Bring the liquid to a simmer, then reduce heat to low. Cover and cook for 90 to 120 minutes until the beef is fork-tender.
In a small bowl, whisk together the cornstarch and cold water to create a smooth slurry.
Slowly stir the slurry into the simmering pot. Continue to cook for 5 minutes until the gravy has thickened to the desired consistency.
Adjust seasoning with salt and pepper to taste before serving over mashed potatoes or egg noodles.