The bi-level dining room at Han Dynasty in Old City is an unremarkable space even under normal circumstances, and rarely have I seen it busy. But given the evening's event, it seemed especially empty when we arrived at five minutes before the 7 p.m. start time on Monday night.

So it was mildly startling when Han Chiang suddenly whooshed out from the shadows, his dark hair tousled, his broken glasses Scotch-taped and tilted askew, with a clipboard in his hand and a most officious tone to his question: "Do you have a reservation?"

The big dinner, it turns out, was downstairs in the party room, a narrow space lined with tables and already filling up with 70-plus diners buzzing with anticipation of an epic Sichuan banquet.

The growing renown of Han Dynasty's blow-out feasts - 20 courses for $25 the first Monday of every month - has cultivated a following among adventure eaters, spice-seekers, and an international crowd craving an authentic taste of home. One of the blog-savvy East Asian Wharton students at my round table seemed particularly tickled to meet Han himself, the famously bossy, opinionated, and amusing owner.

"Oh my God, you're Han?!" he said. "You're a legend!"

"No," protested Han without missing a beat as he delivered an opening salvo of ox tongue and tripe that shined with an orange chili-oil glow. "I'm not dead yet."

That's an understatement for Han, the 31-year-old Taiwanese dynamo who, in the last three years, has channeled the fiery flavors of his father's native Sichuan into a trio of the area's most exciting Chinese restaurants. I first encountered Han last year at his Royersford location, his second, where his chefs turned out vivid tea-smoked duck and fire-licked dry pots - but also Americanized dishes that made Han curse aloud his own occasional suburban compromise.

Such transgressions have been virtually nonexistent at his city debut, where the spice levels can be dialed up to vision-stoking heats, house-steeped chili oil flows like butter in a French restaurant, and you're likely to encounter anything from rabbit and offal to a special called "Weird Taste Chicken." Han Dynasty's menu is not for the squeamish or delicate palate. But for those who love food with intensity, Dynasty's veteran chef, Shao Lin Jiang, 62, is your Sichuan man.

At various meals in recent months, he's cooked perhaps the best fried soft-shell crabs I've ever eaten, streaked with a "hot pot" sauce that radiated a swirling, ethereal spice. Pork in wine and pickled chile sauce crunched against ribbons of white garlic chives. Crispy whole sea bass came braised in a gingery red puree ripe with hot bean paste. The fresh heat of long green peppers snapped against the sweet black richness of beef strips shined in oyster sauce, sesame, oil and soy. Tender threads of "cumin-style" lamb practically exploded on my palate with a musky spice and potent lingering burn. By comparison, the crunchy chips of raw garlic with the Taiwanese sausages were almost sweet and fruity.

The food here had been so consistently thrilling that, even before the Monday banquet, I felt a rare three-bell enthusiasm stoking for a place that lacks much in the way of ambience. But Han, the impresario, proved with this blowout feast to be a master conductor of the multi-course extravaganza, leading us on a journey of subtly varied flavors, textures, and tongue-blazing sensations that amounted to one of the most memorable meals I've eaten this year.

Especially impressive was his command of Sichuan's distinctively numbing spice (ma la) as something of a culinary emotion, making our taste buds wince at the heat then letting them hum across a mild plateau, before rising and falling again over the evening's many crests.

He lit the fuse with the quick spark of fui qi fei pian, a salad of sliced tripe and ox tongue whose chilled temperature belied the swelling heat of its chili-oil glaze, which, with its peppercorn lift and roasty pepper buzz, ignited taste receptors I never knew existed. The dish named "Weird Taste Chicken" circled back in other directions, the tender dark meat touching deep sweetness, nutty sesame, a fermented black vinegar tang with fresh garlic spice.

A plate of "spicy crunchy" cucumbers was so cold, farm-fresh, and sweet that each chunk was a quenching burst of relief.

Steamed rabbit arrived in bony chunks that brought us to a slower pace - but in the lingering process of stripping each morsel of meat, the black bean-chili-peanut sauce unfurled its flavors like an earthy Sichuan mole. The next course brought another respite from the prickly heat - chilled sesame noodles, tanged with vinegar, creamed with sesame paste and minced garlic that added subtle crunch.

Then came duck soup with baby turnips and beads of chili oil that distilled the intensity of a dozen slow-steeped birds. Chilled translucent noodles made from jellied bean flour segued into another Sichuan pasta classic, a warm nest of dan dan noodles twirled into crumbled pork and a heat-balm of chili oil and sesame paste. For some, it wasn't enough.

"Hey, I'm not sweating at all!" my Singaporean tablemate boldly pronounced. And he was right. Han was holding back - but not for long.

Flash-fried cubes of juicy chicken came tossed with a three kinds of peppers, each adding a different briquette to the flame. Pickled chiles, tea leaves, and ginger lent the curiosity of pork kidneys an unexpectedly irresistible savor. Tender pork belly ribbons tangled with fermented black beans and stir-fried leeks for another moment of vegetal sweetness, then - Boom! The beef in dry pot landed like a peppercorn grenade, each chew of tender meat and snappy bamboo shoot releasing a sinus-clearing burst of spice. A trickle of sweat rolled down past my ear. Somewhere in the room, a baby started crying.

And then came flounder in hot sauce, ratcheting up with peppercorn oil and chile flakes to yet another level of painful pleasure. And yet amazingly, despite the intensity of the sauce that smothered them, the sweet delicacy of those fillets was heightened.

Our mouth-numbing apex reached, our bellies well past full, the table erupted in a collective cheer of relief as Han appeared with the intended final dish: honey-walnut shrimp, a treat of crisply fried crustaceans glazed in a lemony sparkling wine-mayo so delicately sweet, it was the equivalent of candy.

Shrimp for dessert? An exotic feast for the ages in an Old City basement? The element of surprise may be Han Dynasty's most thrilling spice of all.