Sear the Short Ribs:
Season the short ribs generously with salt and pepper.
Heat the olive oil in a large skillet over medium-high heat.
Brown the short ribs on all sides for 3-4 minutes per side, until they develop a nice crust.
Remove the short ribs from the skillet and set them aside.
Prepare the Slow Cooker:
In the same skillet, add the chopped onion and minced garlic, and sauté for about 2-3 minutes, until softened.
Add the tomato paste to the onions and garlic, stirring for another minute to combine.
Pour in the beef broth, red wine (if using), Worcestershire sauce, soy sauce, and fresh thyme. Stir to combine and scrape any browned bits from the skillet.
Transfer the liquid mixture into the slow cooker.
Slow Cook the Ribs:
Place the seared short ribs into the slow cooker, making sure they are submerged in the liquid.
Add the bay leaf.
Cover the slow cooker and cook on low for 6-8 hours, or until the short ribs are tender and the meat easily pulls away from the bone.
Cook the Rice:
While the short ribs are cooking, prepare the white rice.
In a medium saucepan, bring the water or broth to a boil.
Stir in the rice, salt, and butter (if using).
Reduce the heat to low, cover, and let the rice cook for about 15-20 minutes, or until the rice is tender and the liquid is absorbed.
Fluff the rice with a fork before serving.
Assemble the Dish:
Once the short ribs are done cooking, carefully remove them from the slow cooker and discard the bay leaf.
Shred the meat from the bones or serve the ribs whole, depending on your preference.
Spoon a portion of rice onto each plate and top with the tender short ribs and a generous amount of the savory sauce from the slow cooker.