The old rhyme goes that couscous is a dish so nice they named it twice. Truthfully, it hasn’t always been that good.

“When I say couscous … you probably think of something that comes in a box,” Gadi Peleg, owner of Flatiron Middle Eastern restaurant Nur, tells The Post.

Not so at Nur: “This is my box,” says the restaurant’s chef de cuisine, Ofir Horesh, proudly holding up a bag of coarse semolina flour.

Every day, Horesh or the restaurant’s executive chef, Meir Adoni, begin the hourslong process of making their fluffy-as-a-cloud, flavor-packed couscous. They steam the flour over vegetable broth until the grains plump up like rice, then pass it through a sieve to keep the consistency from getting clumpy. They repeat the process after an hour of steaming, and then steam it again.

A growing number of restaurants are bringing back the pantry mainstay from the depths of packaged-food purgatory with regionally inspired spins that speak to the grain’s cross-continental roots. And this nouveau couscous is no bland side dish — it’s a main attraction.

Adoni’s version, praised by food critics, is served two ways: with seared lamb chops and roasted carrots, or with a colorful array of vegetables. Both dishes come with a dollop of tershi, a savory pumpkin condiment widely used in Libyan cuisine.

“We zhoozh it up, but this is peasant food,” Peleg says. “We just want to convince people that couscous is not this rock of food sitting in your stomach.”

Couscous can assume different forms depending on its region of origin. In June, chef Einat Admony opened a culinary temple to North African couscous called Kish-Kash, in the West Village, named after the sieve that couscous traditionally passes through after steaming.

Admony grew up in Tel Aviv, Israel, where homemade couscous was prepared on Tuesdays and Fridays. Now, she says, the tradition has waned worldwide, turning good couscous into something of a rarity. “You can’t even find it [in restaurants] in Morocco now,” she says. “I know that if another generation went by, nobody would [make] it.”

Kish-Kash is keeping the custom alive by serving couscous at least six ways, including topped with slide-off-the-bone chicken bathed in olives and a tart lemon sauce. Admony’s airy version is made similarly to Nur’s, but steamed over water instead of broth to keep it from clashing with the menu’s complex flavors.

Lebanese restaurant Au Za’atar in Alphabet City offers yet another regional riff: moghrabieh, which incorporates pearled couscous (made by sauteing the semolina in olive oil) with stewed meats and onion, all doused in a rich meat-based broth. The resulting feast is the star of the menu, says Au Za’atar chef Tarik Fallous, rather than relegated as a side.

“It’s made the same way mothers and grandmothers once made it at home for their families,” he says. “It’s a main dish.”

The best thing about couscous is its versatility — it’s a tasty canvas for tons of different flavors, says Kish-Kash owner Einat Admony. To make authentic couscous in your kitchen, start by adding small amounts of water to semolina, mixing with your hands, until the grains take on the consistency of slightly damp sand. Transfer to a stainless-steel dim-sum steamer, cover with a moist kitchen towel and steam until fluffy, about 1 hour. Then try one of these simple, chef-approved toppings.

Peppery punch: “A nice harissa is always good” for spicing up a bowl of couscous, Nur chef Meir Adoni tells The Post. Simply stir in a spoonful of the chili paste, adding more to taste for extra heat.

Savory sweetness: Admony tosses her couscous with fried garlic, chopped toasted almonds, chopped dried apricots and currants, finishing with a dash of cumin and drizzle of olive oil.

Fall flavor: For an autumnal couscous topper, Au Za’atar chef Tarik Fallous suggests tossing cubed pumpkin in olive oil then roasting until blistered, about 20 minutes, and sprinkling with fresh za’atar spice.