Mashed sweet potatoes. Hold off on the marshmallows and you have a dish that’s vegan, vegetarian and gluten-free (iStockPhoto)

Years ago, my husband and I hosted a holiday party. We thought we had put together a nice array of food. But midway through I noticed a guest whom I hadn’t known very long surveying the spread with skepticism. Turned out she was a vegetarian, and, to my dismay, our holiday table had little to offer her.

I’ve been revisiting that scene in my mind as I think about this year’s holiday festivities, starting with Thanksgiving. If I were hosting a crowd of my current friends on Thursday, there would be not just vegetarians but also vegans and people who can’t eat foods containing gluten. Never again do I want to slight anyone with the food I serve in my home.

But my typical Thanksgiving meal would fall short on all fronts. Our core dishes always include turkey, sausage-spiked stuffing made with store-bought bread, fresh cranberry sauce, mashed potatoes (made with milk and butter) with turkey gravy, candied sweet potatoes, pumpkin pie; we’ve also been known to serve that infamous green-beans-and-mushroom-soup casserole.

For advice as to how to switch things up to accommodate various dietary needs and preferences, I turned to three experts: Elizabeth Turner, editor in chief of Vegetarian Times magazine; Nava Atlas, author of the cookbook “Vegan Holiday Kitchen,” (Sterling, 2011) and Beth Hillson, author of “Gluten-Free Makeovers¨(Da Capo Press, 2011).

Vegetarian version

“In my experience, people are the least attached to the turkey”of all the foods at Thanksgiving, Turner says. “They’re more interested in the mashed potatoes and other side dishes,” some of which (sweet potatoes, green bean casserole, pumpkin pie, cranberry sauce) already are vegetarian-friendly.

That makes planning a vegetarian meal easy, Turner says; just shift your focus from finding a replacement for the big bird toward creating special sides. Here are some tips:

→For stuffing, skip the sausage, add flavor and texture with chestnuts and/or mushrooms, and moisten with vegetable broth. Chestnuts are very special and easy to find this time of year, Turner says. Trader Joe’s has them already cooked and ready to go.

→Start your gravy with a simple roux of flour and butter or margarine, and flavor with mushroom broth.

→For a main dish, serve a veggie-packed shepherd’s pie — “the obvious choice for a newbie vegetarian,” Turner says — topped with standard pie crust or mashed potatoes. For something a bit fancier, try making a vegetable-filled Wellington or potpie using puff pastry. “Most puff pastries are vegan,” Turner says. If you’re vegetarian or vegan, you should always have some in your freezer, she says.

→As for replacing that turkey: More advanced cooks can make seitan “or wheat meat” — a dough made of wheat gluten that you can season and shape however you like. It makes quite a convincing meat alternative “when the dough is seasoned with broth and shaped like a roast or medallions of meat,” Turner says. Or try a “mock meat¨option from companies such as Gardein or Field Roast.

→For “something special for the middle of the table, something that’s pretty,” shape seitan into roulades and stuff with stuffing; bake and serve with cranberry sauce. Or cut seitan into cutlet shapes, bake and top with stuffing and cranberries. “Its turn-key and delicious,” Turner says.

Turner also advises hosts to be aware of “stealth” ingredients that “can creep into recipes” such as turkey or chicken stock, and avoid using them. Alas, those include the marshmallows you plop atop sweet potatoes to candy them. Because they contain gelatin, Turner says, “marshmallows are not vegetarian.”

Vegan, with a vision

Thanksgiving is a harvest feast that originally celebrated the three sister crops: corn, beans and squash, notes Atlas. Those foods and others were traditionally incorporated into main and side dishes alike. “It’s become so turkey-centric, people forget the meaning of the holiday,” she says.

A vegan feast, with no animal products, can easily hearken back to those early traditions, giving vegetables center stage and allowing their flavors to shine, Atlas says. Here are some suggestions:

→For a main dish, serve ravioli with sweet potatoes and sage.

→Roast, bake or mash sweet potatoes; flavor them with real maple syrup, orange juice, thyme, rosemary or some combination thereof.

→Turn to greens. “Everybody loves greens,” from kale and collards to Brussels sprouts, which Atlas calls a “really traditional Thanksgiving vegetable.”

→Make gravy with sauteed onions or shallots and mushrooms; add a good vegetable broth, thicken with cornstarch and flavor with soy sauce or, better yet, with nutritional yeast, a cheesy-tasting ingredient found at health-food stores that provides Vitamin B12, a key nutrient that doesn’t occur naturally in plant-based foods.

→Other sides can include homemade cranberry sauce, a grain- or quinoa-based dish and a pureed butternut squash soup. But consider skipping the green bean casserole. “I could never figure that out,” Atlas says. “Green beans are not a seasonal vegetable right now” and thus might not deserve their place at the Thanksgiving table.

→Bear in mind that vegans don’t eat eggs or dairy products, including butter, milk and cheese, so be careful not to let those products sneak into the meal.

“We share Thanksgiving with a family who does have a turkey,” Atlas says. “But everything aside from the turkey is something everybody can have. The turkey just happens to be sitting there.”

Going gluten-free

Hillson received a diagnosis of celiac disease (an autoimmune disease in which the body rejects gluten, a protein found in wheat, barley and related grains) more than 30 years ago, when she was just 5 years old. She says eating at other people’s homes or at restaurants is challenging because she doesn’t know how gluten-free the food she’s served really is. “It’s not enough to use only gluten-free ingredients,” she explains; if her serving of gluten-free pasta is cooked in water thatħ also was used to cook regular pasta, she’s in trouble.

So when she’s in charge of Thanksgiving, Hillson says, “I’m an advocate of making everything gluten-free.” If that gluten-free food is delicious, she says, “everyone will enjoy it, and you don’t have to single anyone out.” The potential for cross-contamination is greatly reduced, she says.

Crafting a gluten-free Thanksgiving means going through the menu looking for gluten-containing ingredients and swapping them out for gluten-free substitutes. Here are some ideas:

→Use homemade or commercially baked gluten-free bread to make stuffing. (If you are preparing both gluten-free and standard stuffing, Hillson cautions, be sure not to stuff the turkey with the gluten-containing batch. That contact would make the turkey inedible to your gluten-free guests.)

→Use rice flour or a cornstarch slurry instead of wheat flour to thicken pan drippings for gravy.

→If using store-bought stock, check the box or can to be sure it is gluten-free.

→Candied sweet potatoes are fine to serve at your gluten-free feast; marshmallows aren’t vegetarian or vegan, but they are gluten-free.

→In your green bean casserole, substitute homemade cream of mushroom soup or look for store-bought brands that are gluten-free. And instead of canned fried onions, Hillson suggests, dip fresh onion slices into a beaten egg and then in gluten-free flour and bake them on a Pam-sprayed pan. Or, she says, top the casserole with Funyuns. They’re gluten-free.

→ Gluten-free pie crust can be tricky because the gluten in regular flour serves as a “glue” to hold it together, Hillson explains. When making crust with gluten-free flour, try rolling it out between two pieces of plastic wrap. (You can also buy pre-made gluten-free crusts at Whole Foods, she says.) Aside from the crust, pumpkin pie is great and gluten-free, Hillson notes.

And don’t forget the drinks. “Distilled alcohol such as Scotch and bourbon is fine,” Hillson says; the distillation process removes the gluten. And there are at least half a dozen gluten-free beers on the market, she says. “People will be delighted. They are very delicious.”