Seattle vocalist Jennifer Kienzle The setting is Shuga Jazz Bistro. The occasion is a special jam session celebrating the birthday of Seattle pianist Eric Verlinde. Jennifer Kienzle has stepped up to the mic. I’m always struck by her cool finesse and sophisticated ease. She exudes a classic jazz singer aura, all the way down to the little black dress, which she rocks hard I might add. But beneath this impeccable elegance is an underlying sassiness, with a nip of growl. Within…