Preparation

• In a large skillet or Dutch oven, melt 3 tablespoons of butter over medium-low heat. Add the sliced onions and a pinch of salt. Cook slowly, stirring occasionally, for 20-25 minutes, until they become soft, golden, and caramelized. For extra depth, stir in 1 teaspoon of balsamic vinegar or balsamic glaze during the last minute to deglaze the pan. If adding mushrooms, add them in the last 10 minutes of cooking onions.
• While onions are cooking, pat the beef dry and season lightly with pepper. Increase the skillet heat to medium-high, add a drizzle of olive oil and sear the roast on all sides until browned.
• Place the seared roast (or raw, if skipping sear) into your slow cooker or Dutch oven. Scatter the caramelized onions over the top. Sprinkle the Beefy Onion Soup mix packet, then pour in the beef broth (or water). Add thyme sprigs and black pepper. For extra flavor, whisk the Dijon and Worcestershire into the broth before pouring it in.
• Cover and cook on LOW for 7-8 hours or HIGH for 4-5 hours, until the meat is fork-tender. I suggest cooking it only on LOW to achieve the best tenderness.
• Once the roast is done, shred it into large chunks and remove any herb stems. Sprinkle Gruyère evenly over the top. Cover and allow the cheese to melt. If using a Dutch oven, broil for 2-3 minutes until the cheese is melted and bubbly.