• Set your Sous Vide to 185°F in a deep water bath (large saucepan, at minimum).
• In a baking dish, marinate short ribs in 1/4 cup Worcestershire sauce, 1/4 cup beef broth, a sprinkle of fresh thyme and salt and pepper to taste. Set aside.
• 1/4 cup beef broth, a sprinkle of fresh thyme and salt.
• Reduce heat to medium-low and add sugar and 1 tbsp Worcestershire sauce. Mix and simmer for 8-10 more minutes, until onions are golden brown.
• Add minced garlic and cook for 1-2 more minutes.
• In a plastic bag, place marinated short ribs, the liquid, and the caramelized onions, making sure they're evenly distributed.
• Lay flat and seal the bag using a vacuum sealer.
• Place the sealed short ribs in the water bath to cook for 24 hours.

24 Hours Later

• Preheat oven to 375°F.
• Retrieve the short ribs from the water bath and pour the contents into a large bowl. Using your hands or a fork), shred the beef. You may be able to salvage a small bit of the first batch of onions, but they'll mostly be mush.
• Cut 1 onion into thin slices and caramelize with sliced mushrooms in butter for 10 minutes. Add sugar and simmer for another 2-3 minutes until golden brown.
• Prepare a baking dish with cooking spray and line with the bottom half of the buns.
• Place a layer of provolone cheese, a generous layer of shredded beef, a layer of the caramelized onions and mushrooms, and a layer of shredded Gruyere cheese. Top with the other half of the bun.
• Melt 1 tbsp of butter and mix with 3 tbsp of the liquid from the Sous Vide bag, garlic salt, and onion powder.
• Brush the top buns with the mixture and sprinkle with fresh thyme.
• Bake sliders for 10-15 minutes, or until the cheese is melted. Serve hot!