In this particular case, atlets are an assortment of roast, skewered meat, the skewers probably arranged into some elaborate form, say, by sticking them into a large loaf of bread in decorative array. They are "atlets of palates", furthermore, and while this may mean the cook is skewering animal tongue, it's equally likely that it means exactly what it says, and the cook is using palates - probably from a large animal, like a cow.
The word comes from a dense little family of related variants. Many of the words may, in fact, be used to mean the same thing, even as kebab can refer both to the skewer and to the skewered meat.
haslet - The heart, liver, and other edible viscera of an animal, especially hog viscera. (Chiefly used today in the Southern U.S. [Middle English hastelet, from Old French, diminutive of haste, roast meat, spit, perhaps from Latin hasta, spear, or of Germanic origin.] (from the American Heritage Dictionary and Dictionary.com Unabridged, by way of here)
attelet - A slender skewer, usually ornamented at the top, used decoratively, especially in serving garnishes. [French, variant of hâtelet, from Old French hastelet; see haslet.] (from the American Heritage Dictionary, by way of here)
hatelets or atelets sauce - A sauce (such as egg and bread crumbs) used for covering bits
of meat, small birds, or fish, strung on skewers for frying.(from Webster's Revised Unabridged Dictionary, 1913, by way of here) There's a recipe for hatelets (the sauce) in George Augustus Sala's The Thorough Good Cook from 1896.
Those are all forms of the word attested to in English. Hastelet also yields a number of results in French, including that "hastelets des lapereaux", or skewers of rabbit meat, were served to Marie-Antoinette in 1788. The French form was also used by an Italian cookbook Le Re dei Cuochi, or The King of Cooks, published anonymously in 1885. The cookbook includes several recipes for Hatelets, including this one.
Villeroy-style Atlets (Skewered, breaded, deep-fried meat kebabs)The recipe book provides more on Villeroy sauces in the Sauce chapter.
Prepare two small lamb innards (lungs or glands), according to the instructions on p. 170, retrieving them when half cooked. When they are cold, cut them into roundels and the place them in a terrine, together with an equal quantity of roundels of truffles and of scarlet (or bloody) tongue. Add some spoonfuls of finely chopped herbs, prepared and already hot. Leave them to cool, and encase the stakes by threading whem with the roundels of innards, alternating with truffles and tongue. Cover them with Villeroy sauce, and when they are cool, dip them in bread crumbs and fry them. If they are not yet (entirely) cooked, withdraw the stakes and substitute silver ones for them, which are hammered into a base of fried bread, which has been attached to the plate and edged with fried parsley.