Heat 1 tablespoon olive oil in a large Dutch oven over medium-low heat. Add the sliced onions and cook, stirring often, for 25 to 30 minutes until they turn deep golden brown and caramelized.
Push the onions to the side of the pot. Add the remaining tablespoon of olive oil and the beef cubes. Cook the beef until browned on all sides, about 6 to 8 minutes.
Stir in the minced garlic and dried thyme. Cook for 1 minute until fragrant.
Pour in the beef broth and add the bay leaf, salt, and black pepper. Bring the mixture to a simmer.
Add the cubed potatoes. Cover and simmer gently for 45 to 60 minutes, or until the beef and potatoes are tender.
Remove the bay leaf. Use a spoon to mash about one-quarter of the potatoes against the side of the pot, then stir to thicken the broth into a creamy consistency.