Chef Michael Bao’s ambition is plainly visible: The chopstick wrappers and napkins at his newest restaurant both read, “Bún Soho by Michael Bao.” Bún is the latest project in a rapid series of Vietnamese restaurants from the chef, following success at Mai House and Southern California’s Hidden, as well as the hits Bao 111 and Bao Noodles. This one is a small-plates joint that’s both more casual and hipper (read: louder, faster music) than the chef’s other ventures.

The name, pronounced “boon,” denotes the bed of soft, white Vietnamese rice vermicelli that underlies several dishes. So the excellent charred hanger steak ($11) comes spiced and sliced in a bowl, on top of a nest of the noodles and with matchsticks of mouth-wateringly tart green apple. Pour fish sauce over the top and it’s a vibrant, exquisitely balanced little composition. Fiery grilled chicken ($10) and assorted mushrooms ($10) are other appealing options, but the bún and pho bowls are not the best of the bunch. There’s more going on in other small plates, which are, incidentally, easier to share as well.

Plump spring rolls ($6) are filled with bún, avocado, and shreds of salmon, dressed with dill and turmeric, and sent out with a thin, opaque anchovy sauce for dipping. A meaty piece of bass ($12), seared to an impressive surface crisp and dotted with chanterelles, comes with a mild, rich curry sauce and a parsnip purée that’s perked up with coconut and aromatic pandan leaf. Even classics such as fried spring rolls ($9) are excellently done, their crunchy shells stuffed with flavorful minced pork and hints of crab.

The cooking rarely disappoints, but all is not delightful here. Mr. Bao was on the premises each time I ate at Bún, so it doesn’t seem to be a question of an ambitious chef spread too thin to attend to all his properties. But the service staff seems to have been hired for their charisma rather than for their ability and experience. Even when I was the only customer in the restaurant, my simple order was delayed and fumbled; when it starts to get halfway crowded, things fall apart catastrophically. One night we deliberately marked our own order on the paper menu, but that didn’t prevent half of it from getting lost ‘twixt stove and table; meanwhile the restaurant ran out of all beer (“because we only carry two kinds, you know”) and many wines. One Sunday we were offered only a very limited menu, because the kitchen had been so busy the night before it had evidently run out of almost all its ingredients. It’s painful to see food so good so hindered.

One cheerful but inefficient waiter assured us that “mind of pork” was not pork brain. “That’s just what the menu calls it,” he said, as fish fingers aren’t literally the amputated fingers of fish. However, the filling of the firm-jacketed dumplings does have a distinctly neural texture, a telltale unctuousness that made me doubt his explanation. To be sure, Mr. Bao doesn’t shy away from organ meats: One of Bún’s best dishes is doomed to be avoided by the more squeamish clientele — duck hearts and tongues ($9). In a small casserole, the clearly recognizable organs bathe in an anisey seven-spice broth; the hearts mild and firm but not tough, the little tongues wonderfully delicate and rich.

Crumbly Vietnamese blood sausages ($10) come four to an order, beautifully grilled and spiced with hints of ginger. Lamb meatballs ($12) show similar pleasing complexity; they’re meant to be wrapped in lettuce leaves, dunked in fish sauce, and messily enjoyed. Hunks of beef short-rib meat ($10), impaled on stalks of lemongrass, stand out as a rare dish that did not impress me with its deliciousness. The meat is overly fatty and not particularly flavorful, the lemongrass’s contribution purely cosmetic.

Desserts are tropical and $6 apiece. A greenish panna cotta is fine, flavored ever so mildly with pandan, but the other option was so good my tablemates had to talk me down from ordering a second one: hot tapioca pudding rich and sweet with coconut milk and rounds of near-melted banana.

To drink — assuming that the cellar is stocked —there are Tiger and Saigon beers ($5), and half a dozen good sakes, including the very, very good fresh, unpasteurized Dewazakura “Namagenshu” ($42/bottle). Ten wines by the glass include Benton Lane’s juicy pinot gris ($10/$50) and a food-friendly Beaujolais-Villages from Chateau de la Carelle ($8/$31).

Bún’s been open three long months and still has the faltering gait of a newborn; to judge by his relaxed attitude at the height of one evening’s craziness, Mr. Bao seems content with that. Mercifully, the clumsiness doesn’t seem to affect the kitchen’s hearts and minds. I’ll keep going back for the food, but only when I’m feeling particularly patient.

Bún (143 Grand St., between Lafayette and Crosby streets, 212-431-7999).