Ingredients:

  • 2 kg (2.6 lbs) Chuck Steak or stewing beef, trimmed and cut into 2.5 cm (1 inch) cubes
  • 30 ml (2 tbsp) Olive Oil
  • 1 tsp Kosher Salt
  • ½ tsp Freshly Ground Black Pepper
  • 1 tsp Dried Thyme
  • 5 kg (3.3 lbs) Yukon Gold Potatoes, peeled and sliced uniformly thin (approx. 2-3 mm)
  • 1 large Yellow Onion, finely chopped
  • 2 cloves Garlic, minced
  • 60 g (4 tbsp) Unsalted Butter
  • 60 g (½ cup) All-Purpose Flour
  • 500 ml (2 cups) Whole Milk, warmed slightly
  • 250 ml (1 cup) Beef Stock (low sodium)
  • 1 tsp Dijon Mustard
  • ½ tsp Nutmeg
  • 250 g (2 cups) Sharp Cheddar Cheese, grated (divided)
  • 125 g (1 cup) Gruyère or Aged Swiss Cheese, grated (for the topping)

Instructions:

  1. Prep and Sear the Beef: Pat the chuck steak cubes dry and season thoroughly with salt, pepper, and thyme. Heat the oil in a large skillet over high heat. Sear the beef in batches until browned deeply on all sides (2-3 minutes per batch). Transfer seared beef to a clean plate.
  2. Sauté Aromatics: Reduce the heat to medium. Add the chopped onion to the skillet and sauté until softened (about 5 minutes). Add the minced garlic and cook for 1 minute until fragrant. Set aside.
  3. Make the Roux and Sauce: Melt the butter in a clean saucepan. Whisk in the flour and cook for 1-2 minutes to create a smooth roux. Slowly whisk in the warm milk, followed by the beef stock, ensuring no lumps form. Bring to a gentle simmer, whisking constantly, until the sauce thickens enough to coat the back of a spoon (about 5-7 minutes).
  4. Season and Cheese: Remove the sauce from the heat. Stir in Dijon mustard, nutmeg, salt, and pepper. Add three-quarters (3/4) of the Cheddar cheese and stir until completely melted and smooth.
  5. Layer the Gratin: Grease the slow cooker insert lightly. Pour 1/4 of the prepared cheese sauce into the bottom. Create a uniform layer with half of the thinly sliced potatoes.
  6. Add Beef and Onions: Distribute all the seared beef chunks and the sautéed onion/garlic mixture over the first potato layer. Top with the remaining half of the potatoes. Pour the remaining cheese sauce evenly over the top layer.
  7. Slow Cook: Cover the slow cooker. Cook on HIGH for 4 to 5 hours or on LOW for 7 to 8 hours, until the beef is fall-apart tender and potatoes are easily pierced with a fork.
  8. Finish and Broil: If necessary, transfer the gratin to a shallow ovenproof dish. Sprinkle the reserved 1/4 cup of Cheddar and all of the Gruyère (or Swiss) cheese over the top. Place the dish under a preheated grill (broiler) on high for 3 to 5 minutes until the cheese is melted, bubbling, and golden brown. Watch carefully to prevent burning.
  9. Rest and Serve: Allow the gratin to rest for 10-15 minutes after broiling before serving to allow the sauce to set slightly.