Louis Restaurant has been an early morning/very latenight staple for college students and Providence locals for decades. The menu is standard diner fare: eggs any way, hash browns, and fluffy pancakes, in addition to off-menu items like tofu scramble scribbled on sheets of paper posted on the wall. The gruff but warm-hearted waitstaff will make you pretty much anything you want, as long as the ingredients are in the kitchen. That's how a friend of mine ended up with this killer reuben.
The sandwich is served on a soft roll, toasted to preserve bread integrity, and filled with warm corned beef and a generous helping of grilled onions, which are slightly charred and plenty buttery. Several slices of Swiss cheese envelop the meat and onions (lettuce and tomato are optional). The sandwich is so stuffed, closing it is a challenge, even without the addition of the bowl of sauerkraut on the side. The reuben is enough for two meals, but you'll probably end up eating it all in one go.
286 Brook Street, Providence RI 02906 (map); 401-861-5225