Mark Isreal was just a toddler when his grandfather died. But years later, Isreal discovered a gift the elder left to the family: his recipes. One particular dessert, an eggless doughnut, intrigued the baker, and what started as a lark — wholesaling the gooey, organic sweets from a basement — has turned into a booming retail business of exemplary pastries. Now entrenched on Grand Street, Doughnut Plant indulges with delightful flavors such as Valrhona chocolate, ginger, pumpkin, and coconut. Isreal keeps repeat customers guessing by baking different flavors every month or so, but locals anticipate the seasonal specialties: roasted-chestnut doughnuts in November, rose-petal doughnuts around Valentine’s Day, and a blueberry striped version during baseball season. You can get a mouth-watering view of the kitchen through purposely designed portholes and watch the team of bakers at work rolling, dipping, and glazing the treats.