Start by buttering the exterior of all bread slices.
Place the buttered slices for the tops of the sandwiches in a hot pan until golden brown. Remove from the pan and reserve.
Spread Dijon mustard on the bottom slices of the sandwiches and then layer the ham on top of the mustard, followed by 2 slices of the Raclette cheese on top of each sandwich.
Place the two prepared bottom of sandwiches into an oven-safe frying pan, on medium-high heat. Once the bread starts to become golden, take the pan off the heat and place under the broiler to melt the cheese.
Remove the bottom parts of the Raclette Sandwiches from the pan. Cut the cornichon (or gherkins) in half and place them on top of the melted cheese.
Divide the arugula between the two sandwiches, placing it on top of the pickles.
Take the slices of bread which were grilled first, and place them on top of the sandwiches.