In a heavy-bottomed skillet or Dutch oven, melt 2 tablespoons of butter with the olive oil over medium heat. Add the sliced onions and toss to coat.

Reduce heat to medium-low, add salt, and cook the onions slowly, stirring occasionally, until deeply caramelized and dark brown. This takes about 30-45 minutes.

Add the minced garlic and fresh thyme to the caramelized onions. Cook for 1 minute until fragrant. If using wine, pour it in now and scrape up any browned bits on the bottom of the pan.

Add the uncooked rice to the skillet. Stir constantly for 2-3 minutes to toast the rice grains in the butter and onion mixture.

Pour in the beef broth, Worcestershire sauce, and black pepper. Stir well and bring the liquid to a rolling boil over medium-high heat.

Immediately reduce the heat to the lowest setting, cover with a tight-fitting lid, and simmer undisturbed for 20 minutes.

Turn off the heat and let the rice rest, still covered, for 10 minutes. Do not peek!

Remove the lid, fluff the rice gently with a fork, and fold in the remaining 2 tablespoons of butter until melted. Garnish with fresh chopped parsley and serve.