In a large saucepan, melt the butter over medium heat. Add the onion and garlic and cook for 5 minutes, stirring occasionally.
Add the flour and stir until the mixture is thick and bubbly. Gradually add the beef broth, Worcestershire sauce, soy sauce, black pepper, and garlic salt. Bring to a boil, reduce heat, and simmer for 15 minutes.
Meanwhile, in a large skillet over medium heat, brown the ground beef, breaking it up as it cooks. Drain off any excess fat.
Divide the rice into 4 bowls. Top each bowl with a hamburger patty. Fry the eggs in the skillet and place one over each patty. Pour the gravy over the top of each bowl. Serve immediately.
Interesting Facts
The name "Loco Moco" comes from the Hawaiian slang term "loco," meaning "crazy."
The dish is believed to have originated in the 1940s at a café in Hilo, Hawaii, as a quick and inexpensive meal for hungry teenagers.
The original version of the dish included steamed white rice, a hamburger patty, and a fried egg, all topped with brown gravy.