At Rooster Soup, a tuna melt that melts in your mouth, not your hands

One expects an honest cup of soup at the new, dineresque Rooster Soup Co., lighted by ribbons of neon just below Sansom Street's sidewalk, its profits earmarked to feed the city's "most vulnerable."

And, yes, there are soups -- smoked matzo ball, perhaps the finest of the lot, made with stock from the chicken carcasses of Federal Donut's fried birds.

What you don't expect is a cocktail list, corn bread and sausage waffles, and a menu of well-crafted sandwiches. There's a surprisingly bright bacon, latke, and pickled green tomato job.

But even more surprising is chef Erin O'Shea's smart tweak of the tuna melt, the often-soggy lunch counter staple.

Her every step is calculated to avoid its ignoble fate. Unfrozen slabs of sushi-grade tuna are given a kosher salt and celery seed cure, then oil-poached and shredded into a moist (not wet!) salad with chow chow relish, mayo, red onion, celery, dill, cayenne, and chives.

Sturdy slices of custom-made, finely textured challah are (lightly!) griddled. Moons of provolone are (barely!) melted, blessedly creating a moisture shield between the bread and tuna.

The effect? A grown-up tuna melt, ungreasy, modestly juicy, and gently toasted -- anchored by tradition, not sunk by it.

Tuna Melt with cup of soup, $13, Rooster Soup Co., 1526 Sansom St., roostersoupcompany.com, 215 454-6939.

— Rick Nichols