Place the potatoes in a medium pot, cover with water by one inch, add 1 tablespoon salt, and bring to a boil. Simmer for 10 to 15 minutes, until the potatoes are barely tender when tested with a wooden skewer. Drain and cover with a kitchen towel to steam for 5 minutes. Cut in half lengthwise and set aside.
Meanwhile, heat 2 tablespoons olive oil over medium heat in a large (12-inch) sauté pan, add the chorizo, and cook for 8 to 10 minutes, turning often, until browned. Drain all but a tablespoon of the fat from the pan, add the potatoes, and toss to combine with the chorizo and fat. Off the heat, stir in the wine, 1 teaspoon salt, and 1/2 teaspoon pepper.
Divide the sausage and potatoes among four gratin dishes. Arrange the raclette in one layer over the potatoes and chorizo. Distribute the thyme sprigs on top. Bake for 8 to 10 minutes, until the cheese is hot and bubbly.
Remove the gratins from the oven, place the cornichons on top, and serve hot with the bread and mustard.