In retrospect, the branding of Thomas Keller—in the business, not bovine, sense—was to be expected, a predictable crank of the wheel of commerce. But few could have foreseen that it would go this far.

After all, Keller seemed to dwell for years in a Yountville bubble, an isolated and exacting artist, uninterested in expansion or endorsement deals. But when change began in 2004, it did so in earnest. A version of his Yountville bistro, Bouchon, opened in Las Vegas. He recast the French Laundry for an urban setting with Per Se in Manhattan. Talks commenced proposing Keller as a pitchman for All-Clad. The chef and his lamb purveyor, Keith Martin, drew up plans to market specialty cuts to upscale groceries.

Even as Keller spread himself thin, the food world continued to lay it on thick. The chef earned four stars here (San Francisco), five stars there (Mobil Travel Guide), and the rare three-star ranking for French Laundry and Per Se in the Michelin guides to San Francisco and New York, respectively. His reputation remained stratospheric, but many began to wonder whether the wine country’s Picasso was morphing into Wolfgang Puck. What ever happened to little Tommy Keller from the neighborhood?

The answer is, he’s back in the town where he grew famous. His new restaurant, Ad Hoc, comes wrapped in a prix fixe package, special delivery to the common man. Unlike the royalist French Laundry, this is a willfully populist restaurant, so come-as-you-are in its attitude that when it opened in September it had a no-reservations policy. (Ad Hoc now takes them, but they’re not required.) Waiters wear jeans, canvas sneakers, and throwback short-sleeve mechanic’s shirts: grease monkeys stained with extra virgin olive oil. The sound track leans toward Eric Clapton hits and “Hotel California.” Like the Olive Garden, the restaurant has a slogan, emblazoned on a banner by the entrance—“For the Temporary Relief from Hunger”—cutesy enough to cause the temporary loss of appetite.

This is something of an inside joke. Keller calls Ad Hoc a “temporary” restaurant, a place to tide us over for the next few months until the chef can open what he says he has always wanted: a restaurant serving burgers and half-bottles of wine. Maybe that will happen. But enough forethought lies behind Ad Hoc to make it feel like something meant to linger. Is it really just a stand-in or more a trial run?

Whatever the case, the concept is cool enough to keep around. Like Chez Panisse, Ad Hoc daily offers a changing prix fixe menu, the big difference being that the four courses come family-style. A recent meal began when a waiter plunked down a wooden salad bowl brimming with spinach, black olives, goat cheese, toasted pine nuts, and sweet orange segments. Another plunk produced a cruet of citrus vinaigrette—a lovely, lively dressing that diners drizzle onto the greens. Later that week, the self-service salad came with the same dressing, but sweet gems lettuce took the place of spinach, and feta was the starring cheese.

Such easygoing presentations are refreshing in a region abundant in cerebral fare. How nice to get your food without enduring lengthy disquisitions on the pedigree of the pâté. Plus, little appeals more to a patron’s primal urges than, for instance, a heaping platter of braised beef short ribs. Never mind that our ancient forebears rarely served theirs with green lentils, Brussels sprouts, and cipollini onions, or followed them with cornmeal cake beneath a crown of blueberry compote. Ad Hoc echoes the refrain of the American family: It’s dinnertime. Shut up. Let’s eat.

Of course, because it’s Thomas Keller, even comfort food, however casually delivered, comes with expectations, the promise of a sprinkling of magic dust. Occasionally, such hopes are met. Monkfish, pan roasted and perfumed with thyme, drifted in on a platter laden with romesco sauce and saffron rice. Amid the fillets were large hunks of leek, slow-cooked sous vide to a melting texture without an overdose of butter. You could spend a lifetime searching for a better dish.

Just as often, though, Ad Hoc presents a Keller that the skilled home cook can imitate, as with sautéed duck breast with the pedestrian pairing of autumn squash and Brussels sprouts. Tender but lacking gamy flavor, the meat offered little but a blast of butter. The dish’s saving grace was a bed of crunchy black rice.

Those who demand more of a Keller restaurant can’t fairly do so for less than $45, the price per person at Ad Hoc. Nor could they ask for a more fitting wine list than this compact compilation, which covers nine countries and features only bottles under 30 bucks.

Besides, crying for something different might be missing the point. On a recent evening, while pausing to accommodate a dessert request (the menu, though set, is not entirely unbending), our waiter offered this prediction: Ad Hoc would remain in Yountville, and the model would later be rolled out in other cities. That may require cloning Thomas Keller. But, this being a free market, you get the feeling that someone will.

Ad Hoc 6476 WASHINGTON ST. (At OAK CIR.), YOUNTVILLE, 707-944-2487. DINNER ONLY, THURS.–MON. RESERVATIONS RECOMMENDED. WHEELCHAIR ACCESSIBLE. $$$. ★★½