One of the 20 or so courses served to me the first time I ate at the new Aska in Brooklyn was a cluster of nasturtium leaves, next to a bundle of burned herb sprigs and flower stalks, tied up with a string. It looked pretty and pagan at the same time, like a page from a Martha Stewart lifestyle magazine for witches.

This plate was more than just photogenic, though. Wrapped inside the scorched bouquet was a langoustine, very gently cooked to a soft pink. It tasted of herbs and ashes. There were blots of chamomile jelly and a langoustine-head sauce on the plate, too, and when I rubbed a bit of the orange-pink lobster around in there, the combination of flower and shellfish flavors was a complete surprise, extraordinary in ways I’d never imagined before.

One of the rewards of working as a restaurant critic for a few years is getting to see chefs growing into their ambitions. On my watch, few have done this as dramatically and successfully as Aska’s chef, Fredrik Berselius. Aska, which opened beneath the ribs of the Williamsburg Bridge in July, is his third restaurant. And with each fresh incarnation, his cooking has taken a leap forward.

His first, in 2012, was a part-time operation called Frej, which shared its space in Williamsburg with a ramen outfit and a coffee bar. Its five-course menu was a great deal at $45, and Mr. Berselius, who was born and raised in Sweden, was already showing a gift for delicately naturalistic compositions in the New Nordic style. But some of the flavors were tentative, like underexposed photographs.