The regional table / Delaware
Chicken and Slippery Dumplings, Rolled Flat and Boiled in the Broth
The whole argument is in the rolling pin: this dumpling is rolled flat, cut square and boiled in the broth, and it never sees a spoonful of baking powder.
The clearest statement of the difference I can point to was printed by a reader rather than a cookbook. On 2 October 1976 the recipe exchange column in Lancaster Farming carried a request from a man who had eaten the dish years before and could not find it written down: he had plenty of recipes for the biscuit type of dumpling served with chicken in most places, he said, but the slippery type were more like a thick noodle, chewy and delicious. Six weeks later, on 13 November, the answers ran. One of them is headed simply Slippery Dumplings and comes from Mrs. Frank Allen of Mardela Springs, in Wicomico County, Maryland, a few miles west of the Delaware line: two cups of flour, a pinch of salt, a tablespoon of shortening or lard, hot water enough to make the dough slightly sticky, rolled thin on a well floured board, cut in squares and dropped into the liquid with the pot stirred from the bottom so nothing sticks. No egg. No leavening. Her one piece of advice is that the more you work the dough the better the dumplings, which is the opposite of everything said about biscuit dough, and that is the point. Printed a few inches away in the same column is a Chicken and Dumplings from Felton, Pennsylvania, whose dough squares carry a teaspoon of baking powder, and a Spatzen or Slippery Dumplings from Allentown that is a thin batter sliced off a board into boiling water. One word, three different things, on one newspaper page.
The technique is far older than the name, and the mid-Atlantic books print it without ever using the word. Mrs. Rorer's Philadelphia Cook Book of 1886 has both shapes and keeps them apart without seeming to notice: her Stew of Beef with Dumplings sifts a heaping teaspoonful of baking powder into a pint of flour, drops the soft dough onto the meat by small spoonfuls and warns you not to uncover the saucepan while the dumplings are cooking, or they will fall immediately — while her Chicken Pot-pie rolls its paste into a thin sheet, cuts the trimmings into squares, layers them with the chicken and the potatoes and simmers the lot for an hour and a half. Raised and dropped on one page, flat and boiled on another. Closer to home the record thins out fast, and it is worth saying plainly how thin. The one pre-1930 Delmarva community cookbook I could reach is The Eastern Shore Cook Book of Maryland Recipes, compiled by the Epworth League of the Still Pond Methodist Episcopal Church in Kent County, published June 1916, revised December 1919, and printed in Wilmington, Delaware by Hubert A. Roop of 604 Market Street: it prints Drop Dumplings of egg, milk and baking powder dropped by the teaspoonful into hot gravy, Noodles rolled very thin and hung up to dry, and a bean soup that tells you to add drop dumplings or noodles — and not one slippery dumpling. The Trinity Parish Cook Book, put out by the Ladies' Parish Aid Society of Trinity Church in Wilmington in 1892, has no dumpling of any kind in it. Fifty Years in a Maryland Kitchen, 1881, never uses the word slippery at all, and its soup dumplings are dropped. The name itself I cannot find in print before the 1970s: it draws a blank in the Georgia, Nebraska and South Carolina newspaper archives, the Pennsylvania archive holds exactly three pages carrying it, and the Virginia end of the peninsula could not be tested because Virginia Chronicle refuses automated requests. What the Pennsylvania run does give is Delaware itself. On 8 September 1984 the same paper followed a British 4-H exchange visitor through a downstate stay in Sussex County, with the Murray family of Frankford, and listed what she had eaten: squash, pumpkin and blueberry pies, clams, and chicken and slippery dumplings, which were another hit. The quantities below are worked out for this page around Mrs. Allen's dough, which is the part that was written down.
Why this version works
Hot water in the dough. Hot water softens the flour and relaxes the dough enough to roll thin without springing back, which is why Mrs. Allen's recipe calls for it and why working the dough hard makes her dumplings better rather than tough. A cold-water dough fights the pin and shrinks on the board.
Rolled thin, cut square. An eighth of an inch is thin enough that the middle of the square is done at the same time as its edges, and wide enough that the pieces overlap in the bowl instead of dispersing. A square also costs nothing to cut: you roll, you run a knife across twice, and there is no rerolling of scraps.
No leavening in the dough. Baking powder is the entire difference between the two dishes. It inflates the dough into a wet biscuit that sits on the surface and must be steamed under a lid; leave it out and the square stays flat, cooks through in the liquid, and comes out dense and chewy rather than cakey.
Boiled in the broth, not in water. The loose flour on the squares washes into the pot and thickens it, so the broth finishes somewhere between soup and gravy with no roux and no slurry. That same starch is what makes the surface of a cooked dumpling slick — the name is a description of what your spoon runs over, not a compliment.