Love a Reuben. My favorite sandwich ever. Using good shredded corn beef will make your sandwich go from good to amazing.
Heat a frying pan on the stove top to medium heat. Spread 1/2 the butter on the outsides of each piece of bread.
Place the bread slices butter-side down and spread the dressing on both pieces. Top one slice with the corned beef, sauerkraut, then the swiss cheese. Take the last slice of bread and place on top butter side up.
Place sandwich in frying pan and grill each side till it is golden brown and the center is hot, about 4 minuets per side. Serve with fries.