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There are many delicious things with which you could embellish a McDonald’s Filet-O-Fish sandwich — if your goal was to make it even more calamitous to the waistlines of the general Filet-O-Fish-loving public than it already is. A Scotch egg, a pound of bacon, or a deep-fried Snickers bar all spring to mind. But if you really wanted to go all out, if you really wanted to vex the fast-food police, what you might do is simply plop an additional Filet-O-Fish on top of the first one.

That may have been the thinking behind the new Double Filet-O-Fish, which recently made its debut at several Mickey D’s throughout the city. The sandwich is, in what McDonald’s headquarters calls a limited engagement, loosely timed to coincide with Lent, so when the Underground Gourmet — a Filet-O-Fish fan since the days when he still wore short pants — found out about it, he hurried on over to the nearest location to give it a try, and with something like a Proustian shiver shooting down his spine, stepped up to the counter.

Although the UG’s dining companion refused to sample it — stating that she’d just as soon eat a rat-licked Taco Bell taco or chew on broken glass than partake of this tartar-sauced slopfest — the UG plunged right in. Besides the obvious, the difference between a regular single Filet-O-Fish and a double, the UG learned, is that the single contains a minimalist half-slice of melted American cheese, whereas with the double, you get a whole slice. Also, about twenty minutes later, you feel roughly twice as bad. But it’s a good bad. — Rob Patronite and Robin Raisfeld

At participating McDonald’s, including 14 E. 47th St., nr. Madison Ave., and 39 Union Sq. W., nr. 17th St.