I've used parsnips in stews but not for much else. However, my characters might just find them useful. This information comes from "Science in the Kitchen." ©1893
Description. — The common garden parsnip is derived by cultivation from the wild parsnip, indigenous to many parts of Europe and the north of Asia, and cultivated since Roman times. It is not only used for culinary purposes, but a wine is made from it. In the north of Ireland a table beer is brewed from its fermented product and hops.
The percentage of nutritive elements contained in the parsnip is very small; so small, indeed, that one pound of parsnips affords hardly one fifth of an ounce of nitrogenous or muscleforming material. The time required for its digestion, varies from two and one half to three and one half hours.
Preparation and Cooking. — Wash and trim off any rough portions: scrape well with a knife to remove the skins, and drop at once into cold water to prevent discoloration. If the parsnips are smooth-skinned, fresh, and too small to need dividing, they need only be washed thoroughly before cooking, as the skins can be easily removed by rubbing with a clean towel. Reject those that are wilted, pithy, coarse, or stringy. Large parsnips should be divided, for if cooked whole, the outside is likely to become soft before the center is tender. They may be either split lengthwise or sliced. Parsnips may be boiled, baked, or steamed; but like all other vegetables containing a large percentage of water, are preferable steamed or baked.
The time required for cooking young parsnips, is about forty-five minutes; when old, they require from one to two hours.
Baked Parsnips.—Wash thoroughly, but do not scrape the roots; bake the same as potatoes. When tender, remove the skins, slice, and serve with cream or an egg sauce prepared as directed for Parsnips with Egg Sauce. They are also very nice mashed and seasoned with cream. Baked and steamed parsnips are far sweeter than boiled ones.
Baked Parsnips No. 2. — Wash, scrape, and divide; drop into boiling water, a little more than sufficient to cook them, and boil gently till thoroughly tender. There should remain about one half pint of the liquor when the parsnips are done. Arrange on an earthen plate or shallow pudding dish, not more than one layer deep; cover with the juice, and bake, basting frequently until the juice is all absorbed, and the parsnips delicately browned. Serve at once.
Boiled Parsnips. — Clean, scrape, drop into a small quantity of boiling water, and cook until they can be easily pierced with a fork. Drain thoroughly, cut the parsnips in slices, and mash or serve with a white sauce, to which a little lemon juice may be added if desired.
Browned Parsnips. — Slice cold parsnips into rather thick pieces, and brown as directed for browned potatoes.
Creamed Parsnips.— Bake or steam the parsnips until tender; slice, add salt if desired, and a cup of thin sweet cream. Let them stew slowly until nearly dry, or if preferred, just boil up once and serve.
Mashed Parsnips. —- Wash and scrape, dropping at once into cold water to prevent discoloration. Slice thinly and steam, or bake whole until perfectly tender. When done, mash until free from lumps, removing all hard or stringy portions; add salt to taste and a few spoonfuls of thick sweet cream, and serve.
Parsnips with Cream Sauce. — Bake as previously directed. When tender, slice, cut into cubes, and pour over them a cream sauce prepared as for Turnips with Cream Sauce. Boil up together once, and serve.
Parsnips with Egg- Sauce. — Scrape, wash, and slice thinly, enough parsnips to make three pints; steam, bake, or boil them until very tender. If boiled, turn into a colander and drain well. Have ready an egg sauce, for preparing which heat a pint of rich milk or very thin cream to boiling, stir into it a level tablespoonful of flour rubbed smooth with a little milk. Let this boil a few minutes, stirring constantly until the flour is well cooked and the sauce thickened; then add slowly the well-beaten yolk of one egg, stirring rapidly so that it shall be well mingled with the whole; add salt to taste; let it boil up once, pour over the parsnips, and serve. The sauce should be of the consistency of thick cream.
Parsnips with Potatoes.—Wash, scrape, and slice enough parsnips to make two and a half quarts. Pare and slice enough potatoes to make one pint. Cook together in a small quantity of water. When tender, mash smoothly, add salt, the yolks of two eggs well beaten, and a cup of rich milk. Beat well together, put into an earthen or china dish, and brown lightly in the oven.
Stewed Parsnips. — Prepare and boil for a half hour; drain, cover with rich milk, add salt if desired, and stew gently till tender.
Stewed Parsnips with Celery. — Prepare and steam or boil some nice ones until about half done. If boiled, drain thoroughly; add salt if desired, and a tablespoonful of minced celery. Turn rich boiling milk over them, cover, and stew fifteen or twenty minutes, or till perfectly tender.