French Dip Panini

Generously season the roast with salt and pepper. Let stand at room temperature for 1 hour.

Preheat an oven to 425°F.

Place the roast, bone side down, on a rack in a roasting pan. Pour 1 1/2 cups of the broth into the pan. Transfer to the oven and roast for 20 minutes. Reduce the oven temperature to 350°F and continue roasting until the meat is nicely browned and an instant-read thermometer inserted into the center of the meat, away from the bone, registers 125°F, about 45 minutes more.

Transfer the roast to a platter, cover loosely with aluminum foil and let cool to room temperature. Wrap the roast in foil and refrigerate for at least 2 hours or up to overnight. Pour the pan drippings and accumulated juices from the platter into an airtight container, cover and refrigerate until ready to use.

Spoon off any solidified fat from the drippings. In a small saucepan over medium heat, warm the oil. Add the shallot and cook, stirring, until softened, 1 to 2 minutes. Add the drippings, the remaining 1 cup broth, the water and thyme sprig. Bring to a simmer and cook for 3 to 5 minutes. Remove the thyme sprig and discard. Reserve 1 cup of the jus for serving.

Preheat an electric panini press to medium-high according to the manufacturer’s instructions.

Brush the cut sides of the rolls with the melted butter. Working in batches, place the rolls, buttered side down, on the panini press and cook until lightly browned, 3 to 5 minutes. Transfer to a plate.

Remove the bone from the roast. Using a very sharp slicing knife or an electric slicer, thinly slice the beef and divide into 4 equal portions. Dip each portion into the remaining jus and let the excess drip off. Pile the beef onto the bottom halves of the rolls and top with the caramelized onion and cheese, dividing evenly. Cover each with a top half of the roll.

Place 2 sandwiches on the preheated panini press, close the lid and cook until the cheese is melted, 5 to 6 minutes. Transfer to a plate. Repeat to cook the remaining sandwiches. Carefully open the sandwiches and garnish each with 6 to 8 watercress sprigs. Close the sandwiches and serve immediately with ramekins of the reserved jus for dipping. Serves 4.