The downscaling of American fine dining has been a running theme of late, as many of our best chefs have tried to solve the riddle of the second restaurant.

Going casual has generally been the smartest move, especially for a suburban location. But the gambit is a bit more challenging for Susanna Foo, who has probably done as much as any American chef to elevate the image of Chinese food - at least as a starting point for fusion cooking, now so widely imitated as to be part of the mainstream.

Does taking the high-concept cooking down a notch in elegance risk bringing her menu - and her legacy as an innovator - a bit closer to the imitators and acolytes?

Yes, it does. Even the stylish contemporary dining room at Susanna Foo Gourmet Kitchen in Radnor, with its red curtains and columns of layered cultured stone, is vaguely reminiscent of nearby Nectar, where Foo's former chef, Patrick Feury, now cooks. But in the early months of her new Radnor outpost (her only other restaurant since the closing of her Atlantic City venue), it's become clear that even legends go through learning curves.

Of course, there is still plenty of evidence of the special culinary eye that made Foo, now 63, a major figure in East-West cooking to begin with. Crisply fried wontons filled with coriander- and jalapeño-flecked goat cheese are set next to swirls of surprisingly potent Dijon-honey mustard and a cool fan of roasted beets - a vibrant tableau of contrasting spice and sweet, hot and cold, crunch and cream.

Her seafood wonton soup is a supremely delicate rendition of the standard, a crystalline broth that holds gossamer-skinned shrimp wontons over a nest of delicate noodles. A monumentally big short rib, meanwhile, is braised Wuxi-style in Shaoxing wine, rock sugar and star anise, then posed beside a fusion starch of coconut milk polenta.

But why, I wonder, did Foo insist on making sushi, which has become a trademark reflex for every suburban Asiaplex eatery? It would be one thing if the maki-work were stellar, but it's not. The rice is so underseasoned the fish on top tastes flat. The combinations are mundane. The ingredients are high quality, as is obvious in the bigeye tuna sashimi platter, but the presentation has no finesse, with a nearly tasteless tartare that is redundant beside the sashimi.

Foo's strong suit, not surprisingly, is her deep reservoir of updated Chinese flavors. And unlike so many American chefs who draw ideas from cookbooks, TV shows, and stints in better Asian kitchens (like hers), Foo gets her knowledge from the source: from memories of childhood in Mongolia and Taiwan, as well as a series of recent trips to China.

Visits to the meat-loving provinces in the north provided her with the major inspiration for the small plates ("Asian tapas") and dumplings that constitute this menu's most interesting flavors. She's even created a third-floor dumpling atelier above her Walnut Street address where three women from Shanyang make up to 3,000 dumplings a day.

Among the most intriguing are the gingery petite pork ravioli, which look like Chinese tortellini tossed in peppery brown butter. The classics are also a good bet, from the wild mushroom chicken dumplings to the delicate steamed shrimp and chives, and the standard pot stickers. But I'm also partial to the Mongolian lamb pillows, scented with culantro and cumin, that arrive twisted like savory bonbons beneath a soft dice of Asian eggplant.

The Mongolian lamb theme plays out nicely in other dishes, like the fiery stir-fry of Jamison leg meat with scallions and eggplant in black-bean sauce. I also loved skewered strips of lamb satay streaked with herb oil that come encrusted in the surprising texture of whole cumin seeds.

The small-plate format for starters works well in the more casual ambience of the room, where the dark tiger-wood tables go handsomely linen-free, and Foo hopes that large tables and reasonable prices (most entrees about $20 or less) will foster a family-friendly vibe.

The three giant TVs hanging over the room, meant for cooking demonstrations but playing reruns of Emeril Lagasse making hot dogs during one visit, were an incredibly tacky distraction. Foo has wisely turned them off due to complaints.

But there are a number of other things that could still use tweaking - from the uninspired wine list to variations on several Walnut Street standards that are less successful than one might expect.

The crabcakes are so dominated by the flavor of shrimp mousse, they taste more like round shrimp toasts than anything made with crab. The mu shu pork, which I love downtown, has no lily buds, too much smoked tofu, and noticeably not enough pork. Foo's signature crispy duck was uncharacteristically chewy and dry. The Peking pork loins were pounded into such thin pancake crisps, they lost any trace of tender texture.

A surprise delight, however, were the soft shreds of duck confit tossed over rigatoni with a spicy Burmese tomato sauce. A red cabbage slaw mixed with smoked tofu, crushed peanuts and jalapeños was another unexpected winner.

Foo uses spice liberally here, often to great effect, as in the tasty kung pao chicken that anchored a generous lunch box for only $11. That same sauce, flaring with Szechuan peppercorns, lit a wilder fire at dinner beneath succulent tiger shrimp and scallops.

A beautiful miso-marinated black cod, set over Israeli couscous in a lemongrass-coconut broth, had a soft-spoken elegance that was the exception here, not the rule.

The desserts, however, show a refined and imaginative touch, from a silky coconut creme brulee and creamy panna cotta studded with candied ginger to a caramelized banana and chocolate tartlet with rum sauce that was satisfyingly reproduced from the Walnut Street classic.

If only the rest of the second-restaurant riddle were so easy to solve.

Next Sunday, Craig LaBan reviews Snackbar near Rittenhouse Square.

Contact restaurant critic Craig LaBan at 215-854-2682 or claban@phillynews.com. Read his recent work at http://go.philly.com/craiglaban.