One thing I have noticed about tongue is its ability to muffle acidic or sour flavors. Sauces that might taste quite tart with most other things taste so extremely good with tongue. Tongue, smothered in tomatillo sauce. Cold deli-style tongue with lots of horseradish and mustard. Tongue salad, in a very sharp vinaigrette.
This here tongue sandwich operates on much the same principle. It's an adaption of one by chef April Bloomfield. With grilled tongue, she pairs horseradish, bitter greens, and green sauce. It's one of the nicest tongue and sauce combinations I've ever had. It's so good because the acidic sauce is spot-on, a mixture of finely chopped herbs or parsley, with garlic, anchovies, mustard, and lots of red wine vinegar. The original recipe calls for tarragon, but I like it just as much as with sage or parsley.
Bloomfield says of the sauce that it keeps you wanting more and more bites of the tongue, or rather, that every hit of the sour sauce prepares you for another bite of the rich fatty muscle. Makes sense, right?
The original recipe called for grilling the tongue, but lacking a grill, I browned thick slabs of the tongue in my cast iron skillet, until the surface of the tongue was very dark brown and almost crackly, like pork rinds. The sauce cut daggers into the fatty organ, and so I ate slab after slab of the tongue, and was indeed continually interested in doing so.
The sauce is something special. What goes into it? Olive oil, red wine vinegar-soaked bread crumbs, capers, anchovies, minced garlic, tarragon or parsley, and one egg. The last of which is one boiled egg - the yolk crumbled in, the egg white diced for textural contrast. The thick, complex sauce is its own entity rather than a garnish. In fact I could forgo the sandwich altogether and simply eat the tongue with the sauce, which is, of course, what I did with my leftover slabs of tongue.