Jean-Georges Vongerichten is a master of four-star food, but what about the rustic dishes he grew up eating in Alsace? Vongerichten calls his mom for the recipes and shares her secrets with F&W editor Jane Sigal.

Jean-Georges Vongerichten is squeezing the liquid from sugared, diced rhubarb when he's handed a slip of paper. It reads, "Jean-Georges, please call Mom." "Maybe she wants one of my recipes," he says jokingly. "No, she's calling because she wants to make sure I'm doing her recipes right."

Jeannine Vongerichten, the mother of one of the most celebrated chefs on the planet (Jean-Georges owns 15 restaurants, including his recently opened Perry Street in New York City and V and Rama in London), surely knows that her son can cook four-star food. But what about the rhubarb meringue tart he grew up eating in Alsace? Even Jean-Georges isn't entirely confident. "It's a test for me," he admits. "I've never made this tart before."

As his editor at F&W for eight years, I've worked with Jean-Georges on recipes that reflect his inventive blend of French and Asian ideas and ingredients. But today in the kitchen of his flagship restaurant, Jean Georges, in New York City, he's giving me a lesson on the cooking of his homeland in eastern France. Still, he seems to be learning as much as I am.

"My mother said to toss the rhubarb with a handful of sugar," he tells me, "so I wrote down a half cup in the recipe. But the rhubarb is tart. It really needs more sugar."

Jean-Georges is always experimenting, always adapting, even with his mother's recipes. He tastes the sweet liquid that the rhubarb has thrown off and decides it would make a good sorbet. "Here, Danny," he says, handing the bowl of pink juice to Daniel Del Vecchio, his right-hand man. "Take this and churn it. Let's see what happens."

He has already lined a pastry ring with pâte brisée, the basic French pie dough. He spreads the rhubarb in the raw shell. "My mother does it like that," he says. It's a housewife's trick to partially bake the pastry shell and the rhubarb at the same time, saving a step, then add the custard and put the tart back in the oven.

Next, Jean-Georges beats egg whites by hand, gradually adding sugar, until the meringue hangs from the whisk in a soft peak. He spreads the meringue on the tart while it's still warm from the oven, then bakes it a third time. When it re-emerges, the topping is a lovely pale brown.

What's his evaluation of the dessert? "Not bad," he says. "It's nice and tart; just the way I like it." He massages the skin under his chin with thumb and forefinger to show where the tang hits the palate. "I can eat this all day. It's like a great Key lime pie."

Del Vecchio brings the rhubarb sorbet for us to taste—it has a strong vegetal flavor, but it's sweet—while Jean-Georges tells me his family history. The Vongerichtens were originally Van Gerichtens from the Netherlands. Jean-Georges's great-grandfather was a coal handler who transported his merchandise by barge from Lille in northern France, where he lived, to Lyon on the canal that connects two rivers, the Canal du Rhône au Rhin. One year the water froze, and he was stalled in Alsace. He decided to sell the coal on the spot where he had stopped, Illkirsch-Graffenstaden, a suburb of Strasbourg. He built a two-story, white-washed house there in 1832, which is where Georges Vongerichten (Jean-Georges's father) and Jean-Georges and his three siblings were born. The children grew up skating on the frozen canal in winter. Behind the house, Jeannine Vongerichten grew the rhubarb for Jean-Georges's favorite tart.

As Jean-Georges moves on to the next recipe, he notes that the one thing his mother did buy at the market was the famed white asparagus from the nearby town Le Hoetre to make into gratins for family dinners.

Jean-Georges picks up an asparagus spear. "The skin on white asparagus is very tough," he explains. "Not like green asparagus. You need to peel it thickly with a vegetable peeler."

He ties the asparagus spears with kitchen string, five to a bundle, then drops them into a simmering broth. Using a paring knife, he tests the spears for doneness; the blade goes in easily. "White asparagus you want to cook all the way through," he says. "Not like green asparagus. Green you can keep crunchy, but then you should shock it in cold water to keep the color."

Using a fork, he transfers the bundles to a plate and says to Del Vecchio, "Shall we make the old roux?" Jean-Georges adds some of the asparagus cooking liquid to flour whisked into melted butter—he calls using flour "ancient cooking"—then squeezes in a little lemon juice. "They probably didn't add lemon in the old days," he says. "I'm using just a drop to balance the flavors. It's my contribution to the cooking of Alsace."

Then he cuts off the strings on the asparagus, wraps the bundles in sliced Virginia ham and lays them in the gratin dish. In Alsace, he explains, he'd use Black Forest ham. "We have the best pork there is in Alsace."

Jean-Georges clearly appreciates the cooking he grew up with. In 1988, when he was still working at Lafayette in New York, he consulted on an Alsatian restaurant there, De l'Alsace à Brandywine. "My mother came over to help," he says. The New York Times gave the place two stars, but no one was interested in the cooking of Alsace then.

Jean-Georges pours the sauce over the asparagus, sprinkles cheese over the top and seasons the gratin. "Not too much salt," Jean-Georges specifies, "because of the ham." Then he slides the gratin into the oven.

While I linger over the creamy, smoky asparagus, Jean-Georges announces he's going to put a pot of water on for poaching the spaetzle. "I've never seen these spaetzle anywhere but at my house," he says as he starts on the batter. Jean-Georges calls this version "spooned spaetzle" because he shapes the dumpling-size spaetzle with a spoon. He whisks milk into the eggs and flour. "It's too sticky," he says of the mixture. He adds more milk to make it runnier. "I don't know what to say about the consistency, but this is it." It looks like thick pancake batter to me.

He takes spoonfuls of the batter and drops them into the pot; they sink to the bottom. He keeps filling the pot with the batter. As they cook, the spaetzle rise to the top, making room for raw batter at the bottom. Using a Chinese wire skimmer, not a slotted spoon, he moves the floaters to a skillet.

He points to the largest spaetzle in the skillet: "Those are the guys you want to eat. See, no color. You want to leave them nice and white." As he sautés them in butter, he transfers the finished ones to a platter and sprinkles buttered panko over the top, another innovation. "There were no Japanese bread crumbs at my mother's house," he says.

Jean-Georges invites the other cooks in the kitchen to taste what he is making, and there are appreciative murmurs all around. The spaetzle are dense and buttery, and we can't stop eating them. Maybe he'll add them to the menu at one of his restaurants. Or possibly, it's time for him to open yet another restaurant—maybe a new De l'Alsace à Brandywine.