How does one reinvent something as basic as a jelly doughnut? For the past two years, organic baker Mark Isreal has been promising his loyal following at Doughnut Plant that a newfangled jelly doughnut was on the way. Last week, the chalkboard sign outside his Lower East Side bakery finally read “Jelly Doughnuts Are Here!”

Mr. Isreal’s confections are square instead of round, with a hole at the center. Rather than a blob of sugary glop dropped in the middle, these beauties have authentic, organic raspberry filling spread evenly throughout from the first bite until the last. “My original idea was to get the jelly throughout the doughnut but I wouldn’t sell it until it worked perfectly,” Mr. Isreal explained. So for two years, the perfectionist vegetarian baker toiled away, testing machine after machine until he got the doughnut exactly the way he wanted – like a puffy and sweet fruity sandwich.

The creation arrives just in time for Chanukah, when latkes, chocolate coins, and jelly doughnuts are traditional fare. Another variation on an old idea is the doughnut with peanut butter and strawberry jelly, which is just as yummy. Next down the pike, said Mr. Isreal, are custard and Valharona chocolate versions.

Mr. Isreal’s plump and airy $2.50 treats are winter’s answer to heaven. Word on the street is that Martha Stewart, a longtime fan of Mr. Isreal, had a dozen original glazed doughnuts delivered right before her five month lock-up. For the record, Mr. Isreal swears they’re not fattening, as long as you eat only one. Fat chance.

Doughnut Plant, 379 Grand St., 212-505-3700, www.doughnutplant.com.