Chinese pianist Yuja Wang has forged a stellar reputation thus far founded on flashy repertoire. Her Rachmaninov is dazzling, as is her Ravel. Recently though, she has taken steps into meatier, Germanic fare, including her first forays into Beethoven. Rather than take to the nursery slopes, the first Beethoven she has chosen to tackle is the mighty Hammerklavier Sonata, surely the steepest challenge of the 32. Following Schumann's Kreisleriana, it made for a weighty Verbier recital programme which at times felt distinctly like 'work in progress'.

Wang isn't an extrovert performer. Her upright posture is very 'correct' and she rarely leans into the keyboard. Her touch can be exceedingly light, but there's steel in her fingers too, best heard in Ravel's Scarbo – a late substitution for Brahms' First Ballade so as to effect an all ETA Hoffmann-inspired first half. Scarbo is the nightmarish goblin from Hoffmann's Nocturnal Tales who flits and pirouettes through the darkness, his horny fingernails scratching the silk bed-curtains. Here, Wang was diabolical in the best sense of the word, fearlessly hammering the repeated notes and conjuring a terrifying vision before the Will-o'-the-wisp ending where the goblin disappears in a puff of blue smoke.

Before that, Schumann's Kreisleriana had left a mixed impression. Named after Johannes Kreisler, Hoffmann's manic-depressive conductor, it's a lengthy suite of eight movements charting Kreisler's different characteristics. Feathery touches lent poetry, especially to the ruminative inner section of the second movement, but Wang had a tendency to push fast tempos faster and pedalled quite heavily. She tore into the Sehr rasch penultimate movement, cleanly articulated, and created a wonderfully veiled sound in the tripping finale.

Beethoven's Piano Sonata no. 29 in B flat major pushed the boundaries of the piano's capabilities and is monumental in terms of its length, its awe-inspiring power and the challenges it sets the pianist. It is the Everest of Beethoven's sonatas and it's remarkable that Wang scaled its summits with apparent ease. Whether she plunged the work's profound depths is another matter.

She coaxed inner details in the first movement well, and the impish scherzo was played with ferocity, though it lacked crispness. Misgivings grew in the lengthy Adagio sostenuto third movement where Wang created a hushed poise, barely touching the keys, unafraid to test audibility in the Salle's vast tent. It felt fussy and exaggerated, like a Chopin nocturne stretched out to eternity. However, the fourth movement began with a ghostly, exploratory feel and she untangled the knotty fugue well, clearly articulating the different voices to make it skip and dance. Ultimately, Wang's Hammerklavier was an intrepid traversal, but lacks introspection at this early stage.

A couple of glittery encores raised audience spirits: a flashy dazzling Rondo alla Turca – a jazzy conflation of versions by Fazil Say and Arcadi Volodos – drew the biggest cheer of the night, while Wang's slinky playing of Horowitz's gaudy Carmen Variations was breathtaking. This wasn't quite the end of proceedings though. A 'Surprise Concert' followed, featuring many Verbier stars. Wang was joined by Gautier Capuçon to give the world première of Evgeny Kissin's Cello Sonata, a dull, meandering work. Capuçon intoned the mournful lament with luscious tone, while Wang negotiated the sparse piano part via an iPad score.

As an aside, five remote-controlled cameras charted Wang's every move during her recital, displayed on four screens around the Salle des Combins – a very welcome feature that I wish more halls would adopt. In a piano recital, at least half the audience won't be in a position to see the keyboard and the screens add greatly to the concert experience.