Preheat Oven: 400 degrees
Soak the sliced potatoes in salted water for about 20 minutes. In the meantime, bring a medium pot of water to a boil. Drain the potato slices and put them into the boiling water for about 1 minute. Then rinse the slices in cold water and let dry. Put the potato slices in a bowl with olive oil and set aside.
Preheat the oven to 400°F. To make the white sauce, warm the milk and cream over low heat in a small pan. In another pan, melt the butter over medium to low heat and add the flour and stir until smooth and thick, just until it starts to take on a little color. Add the milk and cream slowly, stirring between each addition until smooth. Add salt, pepper and nutmeg to taste. Put the cooked penne pasta in a mixing bowl and add 3/4 of the white sauce and stir. Fill each cocotte or ramekin with 3/4 cup of the white sauce and pasta, and press down with the back of the spoon. Top with a large spoonful of the remaining white sauce. Place each potato slice on the top of every cocotte, overlapping each slightly. Bake until the potatoes lightly brown on the edges. Place a slice of Raclette on the top of each cocotte and return to the oven for another 10 minutes or until the Raclette is melted and lightly browned.
Serve each cocotte, hot, with the cornichon relish on the side.