Place the rice in a fine-mesh strainer and rinse it under cold water until the water runs mostly clear. Drain thoroughly.
Melt 2 tablespoons of butter in a medium saucepan over medium heat. Add the finely diced onion and cook for 3–4 minutes, until softened.
Add the garlic and cook for 30 seconds, stirring constantly.
Add the drained rice, AB’s Steak and Burger Rub, onion powder, and thyme. Toast for 1–2 minutes, stirring until the grains are coated with butter and seasoning.
Pour in the beef broth and optional Worcestershire sauce. Stir once and bring the liquid to a gentle boil.
Reduce the heat to low and cover the saucepan tightly. Cook without lifting the lid for 17–20 minutes, or until the liquid has been absorbed and the rice is tender.
Remove the saucepan from the heat and let the rice rest, covered, for 10 minutes.
While the rice cooks, heat a large skillet over medium-high heat. Add the ground beef and break it into pieces. Cook for 5–7 minutes, allowing some of the beef to remain against the hot skillet long enough to develop browned edges.
Add the diced onion and cook with the beef for 3–4 minutes, until softened. Add the garlic and cook for 30 seconds.
Stir in the onion powder, garlic powder, smoked paprika, seasoned salt, black pepper, and thyme.
If there is excessive grease in the skillet, drain some of it, leaving approximately 2 tablespoons behind.
Sprinkle the flour over the beef. Stir thoroughly and cook for 1–2 minutes to remove the raw flour taste.
Slowly pour in the beef broth while stirring. Add the Worcestershire sauce and beef bouillon, then scrape up the browned bits from the bottom of the skillet.
Bring the mixture to a gentle simmer. Reduce the heat to medium-low and cook for 8–10 minutes, stirring occasionally, until the gravy coats the back of a spoon.
Stir the butter into the gravy. For a creamier finish, add the heavy cream or whole milk. Taste and adjust the seasoning carefully.
Add the remaining 2 tablespoons of butter and the parsley to the rested rice. Fluff gently with a fork and add kosher salt only if needed.
Divide the garlic-butter rice among serving plates and spoon the hot hamburger gravy over the top. Garnish with parsley or green onions if desired.